unfold
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B2 verb /ʌnˈfəʊld/

unfold

展开或打开
Meaning
to open or spread out something that was folded; to gradually reveal or develop
Example
She unfolded the letter carefully.
她小心地展开了信件。
C1 adjective ˌʌn.pəˈtɜːbd

unperturbed

不为某事烦恼或困扰；冷静且镇定
Meaning
Not worried or disturbed by something; calm and composed.
Example
She remained unperturbed despite the challenges.
尽管有挑战，她依然保持冷静。
B2 adjective /ʌnˈrɪəl/

unreal

不真实的
Meaning
not real or not based on reality; exaggerated or imaginary
Example
The experience felt unreal after the sudden news.
突如其来的消息后，这种经历感觉不真实。
B2 adjective /ʌnˈsteɪbəl/

Unstable

不稳定
Meaning
likely to change; not steady or secure; unsteady
Example
The unstable economy made people worried about their jobs.
不稳定的经济让人们担心他们的工作。
C2 adjective /juːˈbɪkwɪtəs/

ubiquitious

无处不在
Meaning
Present, appearing, or found everywhere.
Example
Smartphones have become ubiquitous in modern society.
智能手机已经在现代社会中无处不在。
B2 verb /ˌʌndərˈskɔːr/

underscore

强调
Meaning
to emphasize or highlight something
Example
The incident underscored the need for better safety measures.
这起事件突显了更好安全措施的必要性。
C2 verb /ˌʌndərˈɡɜːrd/

undergird

支持，强化
Meaning
to provide support or foundation for; to strengthen
Example
Strong values undergird a healthy society.
强大的价值观支撑着一个健康的社会。
C1 adjective /ˈʌpərˌmoʊst/

uppermost

最高
Meaning
situated at the highest place or most important
Example
Her family's safety was uppermost in her mind during the crisis.
她在危机期间心里最重要的是家庭的安全。
B2 adjective /ˌʌndərˈlaɪɪŋ/

underlying

基本的
Meaning
basic or hidden but important; forming the foundation of something
Example
The underlying reason for the conflict was never addressed.
冲突的根本原因从未得到解决。
B1 adjective /ˌʌnsəkˈsesfl/

Unsuccessful

失败的; 没有成功的;
Meaning
not achieving desired aims or results; failing to accomplish a purpose
Example
His unsuccessful attempt to climb the mountain left him disappointed.
他未能成功登上山顶，感到失望。
C2 adjective /ʌnˈʌtərəbl/

unutterable

难以言喻
Meaning
Too great, intense, or awful to be expressed or described in words.
Example
She was filled with unutterable joy at the news of her success.
她听到成功的消息时充满了难以形容的喜悦。
C2 adjective /ʌnˈwəʊntɪd/

unwonted

不寻常
Meaning
Unusual, uncommon, or out of the ordinary.
Example
She spoke with an unwonted gentleness that surprised everyone.
她以一种不寻常的温柔说话，令所有人都感到惊讶。
B2 adjective /ʌnˈɑːrmd/

unarmed

手无寸铁
Meaning
Not equipped with or carrying weapons
Example
The police found the suspect unarmed during the search.
警察在搜查过程中发现嫌疑人没有武器。
A2 noun /ˈʌndərweər/

underwear

内衣
Meaning
Clothing worn beneath outer clothes, typically next to the skin.
Example
He bought new underwear for the trip.
他为旅行买了新的内衣。
C1 adjective /ʌnˈfɔːltərɪŋ/

unfaltering

坚定不移
Meaning
Steady and resolute; not weakening or hesitating
Example
She continued with unfaltering determination.
她以坚定不移的决心继续前进。
B1 noun /ˈjuːnjən/

Union

联合
Meaning
the action of joining or combining; a political unit formed from separate states
Example
The union of the two companies created a powerful corporation.
两家公司的联合创造了一个强大的公司。
B2 verb /ˌʌndərˈmaɪn/

undermine

削弱
Meaning
to gradually weaken or damage something or someone
Example
Constant criticism can undermine a child's confidence.
持续的批评可能会削弱孩子的自信心。
B2 adverb /ʌnˈdaʊtɪdli/

undoubtedly

毫无疑问
Meaning
without a doubt, certainly
Example
He is undoubtedly the best player on the team.
他毫无疑问是队里最好的球员。
B2 adverb /ˈɜːrdʒəntli/

urgently

紧急地
Meaning
in a way that requires immediate attention or action
Example
The patient urgently needs medical attention.
病人紧急地需要医疗救助。
C2 adjective /ʌnˈmɪtɪɡeɪtɪd/

unmitigated

完全
Meaning
absolute; not lessened or moderated
Example
The meeting was an unmitigated disaster.
会议是一次完全的灾难。
B1 adjective /ʌnˈkʊkt/

uncooked

生的
Meaning
Not cooked; in a raw state.
Example
Eating uncooked meat can be dangerous.
吃生肉可能是危险的。
B1 adjective ʌnˈplænd

unplanned

未计划的
Meaning
Not planned or arranged in advance; happening spontaneously without preparation.
Example
Unplanned urbanization contributes to environmental issues.
无计划的城市化会加剧环境问题。
C2 adjective /ʌnˈlɛtəd/

unlettered

文盲
Meaning
lacking education or the ability to read and write; illiterate
Example
The unlettered villagers relied on oral traditions to preserve their history.
那些文盲村民依赖口头传统来保存他们的历史。
C1 adjective /ʌnˈwɪtɪŋ/

unwitting

无意的
Meaning
Not aware of what is happening; done without realizing.
Example
She became an unwitting participant in the scam.
她成了这场骗局中的一个无意的参与者。
C2 noun /ˈʌŋkʃən/

unction

涂抹
Meaning
The act of anointing as part of a religious or ceremonial ritual; excessive or insincere flattery.
Example
The priest performed the holy unction with solemnity.
牧师庄重地进行了神圣的涂抹仪式。
B2 adjective /ˌʌndɪˈnaɪəbl/

Undeniable

不容置疑
Meaning
impossible to deny or dispute; clearly true
Example
The evidence of his guilt was undeniable.
他的罪行证据是不容置疑的。
C1 verb /ˌʌndərˈsɛl/

undersell

Meaning
to sell something at a lower price than competitors or to downplay the value of something
Example
The shop undersold its rivals by offering huge discounts.
C2 adjective /ˌʌltrəˈmʌndeɪn/

ultramundane

超凡
Meaning
Relating to things beyond the physical world; supernatural or transcendental.
Example
Philosophers often discuss ultramundane realities beyond human perception.
哲学家们常常讨论超越人类感知的超凡现实。
B1 verb /ˈʌpˌɡreɪd/

upgrade

升级
Meaning
to raise something to a higher standard, improve
Example
We decided to upgrade the software to the latest version.
我们决定将软件升级到最新版本。
B2 adjective /ʌnˈθɪŋkəbl/

Unthinkable

难以想象的
Meaning
impossible to conceive or imagine; beyond belief or consideration
Example
It was unthinkable that such a tragedy could happen in our peaceful town.
在我们和平的小镇上发生这样一场悲剧，简直是难以想象的。
C2 noun /juːˈkeɪs/

ukase

法令
Meaning
An authoritative decree or order, especially one issued by a sovereign or government.
Example
The czar issued a ukase restricting the freedom of the press.
沙皇发布了一项限制新闻自由的法令。
A2 noun /ˈjuːzər/

user

用户
Meaning
a person who uses or operates something
Example
He is a frequent user of this app.
他是这个应用程序的常用用户。
C1 adjective /ˌʌnəˈkaʊntəbl/

unaccountable

无法解释
Meaning
Not able to be explained or justified.
Example
She felt an unaccountable fear as she entered the dark room.
她进入黑暗的房间时感到无法解释的恐惧。
C1 verb /ʌnˈrævəl/

unravel

Meaning
To undo twisted or knitted threads; to solve or explain something complicated.
Example
The detective worked hard to unravel the mystery.
B2 adjective ʌnˈprɛsɪˌdɛntɪd

unprecedented

前所未有
Meaning
Never done or known before; without previous example.
Example
Unprecedented advancements in science changed human lives.
科学上的前所未有的进展改变了人类的生活。
B2 adjective /ʌnˈbaɪəst/

unbiased

公正
Meaning
Not showing prejudice; impartial and fair.
Example
The report gave an unbiased view of the situation.
报告提供了该情况的公正观点。
C1 adjective /ˌjuːnɪˈlætərəl/

Unilateral

单方面
Meaning
one-sided; involving only one party
Example
The country made a unilateral decision to withdraw from the treaty.
这个国家做出了单方面的决定，退出了条约。
C1 adverb /ˌʌnkənˈvɛnʃənəli/

unconventionally

非传统地
Meaning
in a way that is not based on or conforming to accepted standards or norms
Example
She dresses unconventionally, mixing bold colors and patterns that surprise everyone.
她穿着非传统地，混搭大胆的颜色和图案，让每个人都感到惊讶。
C2 verb /ʌpˈbreɪd/

upbraid

斥责
Meaning
To scold or criticize someone harshly.
Example
The teacher upbraided the student for being late again.
老师因为学生再次迟到而训斥了他。
C1 adjective /ˌʌnəkˈnɒlɪdʒd/

unacknowledged

未承认的
Meaning
Not recognized, admitted, or accepted; ignored or unnoticed
Example
Her contributions to the project went unacknowledged.
她对项目的贡献未被承认。
B1 adjective /ʌnˈjuː.ʒu.əl/

Unusual

不寻常; 奇怪;
Meaning
not typical; strange; different from what is normal
Example
She wore an unusual dress to the party.
她穿了一件不寻常的衣服去参加派对。
C1 adjective /ˌʌnsəˈfɪstɪˌkeɪtɪd/

unsophisticated

不复杂
Meaning
Lacking worldly experience, refinement, or complexity.
Example
The villagers led an unsophisticated but happy life.
村民过着简单而幸福的生活。
B2 adjective /ˌʌnɪnˈfɔːrmd/

uninformed

不了解情况的
Meaning
lacking knowledge or awareness about a particular subject; not educated or informed
Example
The decision was made by an uninformed committee.
这个决定是由一个不了解情况的委员会做出的。
B2 adjective /ˈʌt.moʊst/

Utmost

最极; 极限
Meaning
greatest; most extreme; maximum possible
Example
She showed utmost care while handling the fragile items.
她在处理脆弱物品时表现出最大的关心。
C2 adjective /ʌnˈtiːtʃəbəl/

unteachable

不可教的
Meaning
not able or willing to learn; resistant to instruction or guidance
Example
He was so stubborn that he became almost unteachable.
他非常固执，几乎变得不可教。
B2 noun ˈjuːnəti

unity

团结
Meaning
The state of being united or joined as a whole.
Example
Unity among people led to victory.
人们之间的团结带来了胜利。
C1 adjective /ʌnˈkɛmpt/

unkempt

邋遢
Meaning
Having an untidy or disheveled appearance.
Example
He looked unkempt after sleeping outdoors all night.
他睡了一整晚露天后，看起来邋遢。
C1 adjective /ˌʌnbɪˈkʌmɪŋ/

unbecoming

不合适的
Meaning
Not proper or appropriate for a person; unsuitable.
Example
His rude behavior was unbecoming of a leader.
他的粗鲁行为对于一个领导者来说是不合适的。
B1 adverb /ʌnˈfɔːrtʃənətli/

Unfortunately

不幸地
Meaning
used to express regret or disappointment about something
Example
Unfortunately, the weather was bad for our picnic.
很遗憾，天气不适合我们的野餐。
C2 noun /ʌnˈkloʊðɪŋ/

unclothing

脱衣
Meaning
the act or process of removing clothing
Example
The child quickly ran inside for unclothing after playing in the mud.
孩子在泥地玩耍后迅速跑进去脱衣。
C2 adjective /ʌnˈblʌʃɪŋ/

Unblushing

厚颜无耻的; 放肆的
Meaning
showing no shame or embarrassment; boldly shameless
Example
He told the unblushing lie without any hesitation.
他毫不犹豫地说了那个无耻的谎言。
B1 adjective /ʌnˈkaɪnd/

Unkind

残忍; 不友好
Meaning
cruel; not nice or caring toward others
Example
It was unkind of him to make fun of her appearance.
他取笑她的外貌，真是太不友善了。
C2 adjective /ˌʌn.rɪˈdʒɛn.ər.ət/

unregenerate

顽固
Meaning
Not reformed or showing no signs of change; stubbornly refusing to reform or repent.
Example
He remained an unregenerate opponent of progress.
他仍然是进步的顽固反对者。
C1 adjective /ˌʌndərˈhændɪd/

underhanded

阴险
Meaning
acting or done in a dishonest or secret way
Example
They exposed the company's underhanded dealings with its suppliers.
他们揭露了公司与供应商之间的隐秘交易。
C1 verb /ʌpˈruːt/

uproot

拔除
Meaning
To pull something out of the ground; to remove or displace completely.
Example
They uprooted the old tree from the garden.
他们从花园里把老树拔了出来。
C1 adjective /ˌʌnfɔːrθˈkʌmɪŋ/

unforthcoming

不合作的
Meaning
Not willing to talk or provide information; uncooperative.
Example
The witness was unforthcoming about what he had seen.
证人对于他所见的情况不合作。
C2 verb /ʌnˈfrɒk/

unfrock

剥夺神职
Meaning
To remove a priest from his position or deprive someone of a rank.
Example
The corrupt priest was unfrocked after the investigation.
腐败的牧师在调查后被解除职务。
C2 noun /ˈjuːʒəri/

usury

高利贷
Meaning
The practice of lending money at unreasonably high interest rates.
Example
The law strictly prohibits usury.
法律严格禁止高利贷。
B2 adjective /ˌʌnrɪˈlaɪəbl/

Unreliable

不可靠的; 不能被信任或依赖
Meaning
not dependable; not able to be trusted or relied upon
Example
The old car is unreliable and breaks down frequently.
这辆老车不可靠，常常坏掉。
C1 verb /ˌʌndərˈlaɪ/

underlie

位于...之下
Meaning
to be the hidden cause or basis of something
Example
Strong cultural traditions underlie the community's practices.
强大的文化传统是社区实践的基础。
C2 verb /ˈʌndərˌraɪt/

underwrite

Meaning
To guarantee financial support, especially by agreeing to cover losses or risks; in insurance, to assess and accept risks.
Example
The bank agreed to underwrite the company's new bond issue.
B2 adjective /ʌnˈdɪvaɪdɪd/

Undivided

完整的; 完全的; 不分开或不分裂
Meaning
whole; complete; not separated or split
Example
The team showed undivided attention to the coach's instructions.
团队对教练的指示表现出了完整的注意力。
C2 noun juːˈbɪkwɪti

ubiquity

普遍性
Meaning
The fact of appearing everywhere or of being very common.
Example
The ubiquity of smartphones has transformed communication.
智能手机的普遍性改变了通信方式。
B2 adjective /ʌnˈbæləns/

Unbalanced

不平衡的; 不稳定的
Meaning
not balanced; lacking stability or equilibrium; mentally unstable
Example
The unbalanced table kept wobbling.
不平衡的桌子摇晃着。
A2 noun /ˌʌndərˈstændɪŋ/

understanding

理解
Meaning
the ability to grasp the meaning, significance, or nature of something
Example
Her understanding of the issue was impressive.
她对这个问题的理解令人印象深刻。
C1 verb /ˌʌndərˈvæljuː/

undervalue

低估
Meaning
To assign too low a value or importance to something or someone.
Example
She felt that her boss consistently undervalued her contributions.
她感觉到她的老板总是低估她的贡献。
B2 adjective /ʌnˈtʃeɪndʒɪŋ/

unchanging

不变的
Meaning
remaining the same over time; not changing
Example
Her love for her family was unchanging throughout the years.
她对家人的爱多年来始终不变。
C1 adjective /ʌnˈkɒm.prə.maɪ.zɪŋ/

Uncompromising

不妥协, 固执
Meaning
unwilling to change one's views or to agree about something; showing an unwillingness to make concessions to others
Example
He was uncompromising in his demand for a full apology.
他在要求完全道歉时非常坚决。
C1 adjective /ˌjuːtɪlɪˈtɛəriən/

utilitarian

Meaning
Designed to be useful or practical rather than attractive; relating to the doctrine that actions are right if they are useful or for the benefit of a majority.
Example
The building had a simple utilitarian design.
B1 adjective /ʌnˈedjʊkeɪtɪd/

Uneducated

未受教育的; 文盲
Meaning
lacking education; not having received formal schooling or training
Example
Many uneducated workers struggle to find well-paying jobs.
许多未受教育的工人很难找到薪水高的工作。
A1 preposition /ˈʌndər/

under

下
Meaning
in or to a lower position than something
Example
The cat is under the table.
猫在桌子下面。
A2 noun /ˌʌpˈsteəz/

Upstairs

楼上
Meaning
on or to an upper floor of a building; the upper floor or floors
Example
She went upstairs to her bedroom to rest.
她上楼去她的卧室休息。
C1 adjective /ˌʌnɪnˈhɪbɪtɪd/

uninhibited

不受抑制的
Meaning
Not restrained or restricted; free in behavior or expression.
Example
She gave an uninhibited laugh at the joke.
她在笑话中放声大笑。
B2 noun /ʌnˈkɒnʃəsnəs/

unconsciousness

无意识
Meaning
the state of being unaware of and unable to respond to one's surroundings
Example
After the accident, he was in a state of unconsciousness for several hours.
事故后，他昏迷了几个小时。
C2 adjective /ˌʌnrɪˈmɪtɪŋ/

unremitting

不断的
Meaning
Never relaxing or stopping; persistent.
Example
Her unremitting efforts finally paid off.
她不懈的努力终于得到了回报。
C2 adjective /ˌʌnəˈʃʊəd/

unassured

不确定的
Meaning
Lacking confidence or certainty.
Example
She gave an unassured answer during the interview.
她在面试中给出了一个不确定的答案。
C2 verb /ˌʌn.dɪˈsiːv/

undeceive

解惑
Meaning
To free someone from a misconception or false belief.
Example
She tried to undeceive him about the false rumors.
她试图让他摆脱这些错误的谣言。
B2 adjective /ˌʌnəˈveɪləbəl/

unavailable

不可用
Meaning
Not able to be obtained, reached, or used; not present or accessible.
Example
The manager was unavailable to take calls during the meeting.
经理在会议期间不可用，无法接听电话。
C2 adjective /ʌnˈkɒnʃənəbl/

unconscionable

不合理的
Meaning
shockingly unfair or unreasonable
Example
The company made unconscionable profits from the crisis.
公司从危机中获得了不合理的利润。
B2 adjective /ʌnˈwel.kəm/

Unwelcome

不受欢迎的; 不想要的; 不邀请的
Meaning
not wanted or accepted; not invited or pleasant
Example
The unwelcome news ruined their vacation plans.
不受欢迎的消息破坏了他们的度假计划。
C1 noun /ˈʌndərˌstʌdi/

understudy

替身演员
Meaning
An actor who learns another's role to act as a replacement if needed.
Example
The understudy performed when the lead actor fell ill.
当主角生病时，替身演员上场表演。
C1 noun /ʌnkənˈsɜːrn/

Unconcern

漠不关心
Meaning
lack of worry or interest; indifference
Example
She showed complete unconcern about the criticism.
她对批评表现出了完全的漠不关心。
C2 noun/verb /ˈʌpˌkæst/

upcast

向上投掷
Meaning
Verb: To cast or throw upward. Noun: Something thrown or directed upward.
Example
The fisherman upcast his net into the air.
渔夫把他的网投向空中。
C2 noun /ˈjuːzjuːfrʌkt/

usufruct

使用权
Meaning
The legal right to use and enjoy the benefits of someone else’s property without owning it.
Example
The tenant had the usufruct of the land but not its ownership.
租户有权使用这片土地，但没有所有权。
C1 adjective /ˈʌndərhænd/

underhand

阴险
Meaning
done secretly and dishonestly; deceitful
Example
The politician was accused of using underhand tactics to win the election.
那位政治家被指控使用阴险的手段赢得选举。
C2 adjective /ʌnˈɡeɪnli/

ungainly

笨拙
Meaning
Awkward, clumsy, or lacking grace in movement or appearance.
Example
The tall boy moved in an ungainly manner.
那个高个男孩以笨拙的方式走动。
C1 adjective /ˌʌndərɪkˈspoʊzd/

underexposed

曝光不足，忽视的
Meaning
insufficiently exposed to light (in photography) or not given enough attention
Example
The photo was underexposed and looked too dark.
照片曝光不足，看起来太暗了。
C2 adjective /ˌʌnɪmˈpiːtʃəbl/

unimpeachable

无可指摘
Meaning
Not able to be doubted, questioned, or criticized; completely trustworthy.
Example
She is known for her unimpeachable honesty.
她因其无可指摘的诚实而闻名。
C1 noun /ˈʌp.tɜːn/

upturn

改善
Meaning
An improvement or upward trend in a situation, especially in business or economy.
Example
The company experienced an upturn in sales last quarter.
该公司在上个季度销售情况有所改善。
A2 adjective /ʌnˈkʌmf.tə.bəl/

Uncomfortable

不舒服
Meaning
causing or feeling slight pain or physical discomfort; making someone feel embarrassed, awkward, or anxious
Example
The chair was so uncomfortable that I couldn't sit in it for more than ten minutes.
这个椅子太不舒服了，我坐在上面超过十分钟就坐不下来了。
B2 adjective /ˌʌnkənˈtroʊld/

uncontrolled

无法控制的
Meaning
not restrained or managed; lacking control
Example
The wildfire spread in an uncontrolled manner, causing widespread damage.
野火以无法控制的方式蔓延，造成广泛破坏。
C2 verb /ʌnˈkaʊtʃ/

uncouch

从沙发上移开（罕见用法）
Meaning
to remove from a couch or to release from being laid down (rare/archaic usage)
Example
The surgeon attempted to uncouch the cataract.
外科医生试图去除白内障。
B1 adjective /ʌnˈplɛz.ənt/

Unpleasant

令人不悦的
Meaning
not giving or causing pleasure; disagreeable
Example
The medicine had an unpleasant taste.
药物有一种令人不悦的味道。
C1 adjective /ˌʌnɪˈkwɪvəkəl/

unequivocal

明确
Meaning
Leaving no doubt; clear and unambiguous
Example
She gave an unequivocal answer to the question.
她对问题给出了明确的回答。
B2 verb /ʌnˈtaɪ/

untie

解开
Meaning
to loosen or remove a knot or binding; to release something that is tied
Example
She untied the rope to free the boat.
她解开绳子来释放船只。
C1 verb /ˌʌndərˈsteɪt/

understate

低估
Meaning
To describe something as being less important or serious than it really is.
Example
He tends to understate his achievements.
他倾向于低估自己的成就。
A1 adverb /ˈjuː.ʒu.ə.li/

Usually

通常; 一般
Meaning
in most cases; generally; as a rule
Example
I usually wake up at 7 AM every morning.
我通常每天早上7点起床。
B1 adverb /ˌʌpsaɪd ˈdaʊn/

Upside-down

倒过来
Meaning
with the upper part at the bottom; in or into a reversed position
Example
The picture was hanging upside-down on the wall.
图片倒挂在墙上。
C2 verb /ˈʌndərˌmæn/

underman

人员不足
Meaning
to supply with fewer workers or personnel than needed
Example
The hospital was undermanned during the flu outbreak.
医院在流感爆发期间人手不足。
C2 verb /ʌnˈfɛtər/

unfetter

解开束缚
Meaning
to release from restraint or restriction; to free
Example
The new law will unfetter small businesses from excessive regulations.
新法律将使小企业免于过多的规定。
C1 adjective /ʌnˈɒnəd/

unhonoured

未受尊敬的
Meaning
not respected or given the recognition that is deserved; treated without honor
Example
He felt unhonoured after his years of service were ignored.
他的多年服务被忽视后，他感到自己未受尊敬。
C1 adjective /ʌnˈsəʊʃəbl/

unsociable

不合群的
Meaning
not enjoying the company of others; avoiding social interaction
Example
He became unsociable after moving to a new city.
搬到新城市后，他变得不合群。
C1 adjective + noun ʌnˈpresɪdentɪd ˈnɒlɪdʒ

unprecedented knowledge

前所未有的知识
Meaning
Information or understanding that has never been obtained or achieved before.
Example
Artemis will provide unprecedented knowledge about the solar system.
阿尔忏将提供关于太阳系的前所未有的知识。
C1 adjective /ʌnˈtaɪmli/

Untimely

不合时宜
Meaning
happening at an inappropriate or inconvenient time; premature
Example
His untimely death at the age of thirty shocked everyone.
他的过早死亡在30岁时震惊了所有人。
C2 noun /ˈɜːrtʃɪn/

urchin

街头小孩
Meaning
a mischievous or poorly dressed child, often from the streets
Example
The ragged urchins played by the riverbank.
那些穿着破烂的街头小孩在河边玩耍。
C2 noun /ˈjuːnɪvəˌlɛns/

univalence

单价性
Meaning
The state of having a single valence or combining power, especially in chemistry.
Example
Hydrogen is characterized by its univalence in chemical reactions.
氢气在化学反应中以其单价性为特点。
C1 adjective /ˌʌnəˈdɔːrnd/

unadorned

简单的，未装饰的
Meaning
Plain and simple; not decorated.
Example
The room was unadorned, with only a table and a chair.
房间简单，只有一张桌子和一把椅子。
C1 adjective /ʌnˈkʌltʃəd/

Uncultured

不文明的; 无文化的
Meaning
lacking good manners, refinement, or education; uncivilized
Example
His uncultured behavior embarrassed everyone at the dinner party.
他在晚宴上的不文明行为让所有人感到尴尬。
B2 verb /ˈjuːtɪlaɪz/

utilize

利用
Meaning
to make practical or effective use of something
Example
The company aims to utilize solar energy for production.
公司旨在利用太阳能进行生产。
C2 adjective /ˌʌnsɛrəˈmoʊniəs/

unceremonious

不拘礼节/粗鲁
Meaning
Done without formality or courtesy; abrupt or rude.
Example
He made an unceremonious exit from the party.
他从派对上不拘礼节地离开。
C1 adjective /ʌnˈsteɪtɪd/

unstated

未声明
Meaning
not expressed directly in words; implied or left unsaid
Example
The contract included several unstated expectations.
合同包括了几个未声明的期望。
C1 adjective /ʌnˈmænɪdʒəbəl/

Unmanageable

无法控制的; 失控
Meaning
difficult or impossible to control or handle
Example
The large class became unmanageable without proper supervision.
没有适当的监督，班级变得无法控制。
C1 noun /ʌnˈfeɪθfʊlnəs/

unfaithfulness

不忠
Meaning
the quality of being disloyal or not faithful; breach of trust or fidelity
Example
His unfaithfulness led to the end of their marriage.
他的不忠导致了他们婚姻的结束。
C1 adjective /ˌʌnəˈteɪnəbl/

unattainable

无法实现的
Meaning
impossible to achieve, reach, or accomplish
Example
For many, becoming a professional athlete remains an unattainable dream.
对许多人来说，成为职业运动员仍然是一个无法实现的梦想。
B2 adjective /ˌʌnkənˈvɪnsɪŋ/

Unconvincing

不可信
Meaning
failing to persuade or impress; not believable or credible
Example
His excuse for being late was completely unconvincing.
他因迟到而给出的借口完全不可信。
B2 adjective /ʌnˈstɛdi/

unsteady

不稳定的
Meaning
not firm or stable; likely to change or fail
Example
She felt unsteady on her feet after the long journey.
长途旅行后，她感到站立不稳。
C2 adjective /ʌnˈtʃeɪst/

Unchaste

不道德的; 不纯洁的;
Meaning
not celibate; having engaged in sexual relations; lacking moral purity
Example
The conservative society considered her behavior unchaste and improper.
保守的社会认为她的行为不道德和不合适。
B2 adjective /ʌnˈnætʃərəl/

Unnatural

不自然的
Meaning
not existing in nature; artificial; forced
Example
The actor's smile looked unnatural and forced.
演员的笑容看起来很不自然，很勉强。
B2 adjective /ʌnˈriːzənəbəl/

unreasonable

不合理的
Meaning
not guided by reason or fairness; excessive or extreme beyond what is acceptable
Example
The manager made an unreasonable demand that no one could realistically meet.
经理提出了一个不合理的要求。
C2 adjective /juːˈʒʊəriəs/

usurious

高利贷的
Meaning
Charging excessively high interest rates on loans.
Example
The bank was accused of offering loans at usurious rates.
该银行被指控以高利贷利率提供贷款。
B1 adjective /ˈjuːnɪfɔːrm/

Uniform

制服
Meaning
consistent; identical; standardized
Example
All students must wear a uniform to school.
所有学生必须穿制服上学。