undulous
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C2 adjective /ˈʌndjʊləs/

undulous

波浪形的
Meaning
Having a wavy surface or form.
Example
The artist painted the undulous sea at sunset.
艺术家在日落时画了波浪形的海洋。
A2 preposition /əˈpɒn/

upon

之后
Meaning
on or immediately after
Example
Upon hearing the news, he rushed to the hospital.
听到消息后，他赶到医院。
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。
B1 adjective /ˈʌpˌkʌmɪŋ/

upcoming

即将到来
Meaning
about to happen or appear
Example
The upcoming event will be held next week.
即将到来的活动将在下周举行。
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。
C1 adjective /ʌnˈkwes.tʃən.ə.bl̩/

Unquestionable

无可争议的; 确定的
Meaning
not able to be disputed or doubted; certain and beyond doubt
Example
Her honesty and integrity are unquestionable qualities.
她的诚实和正直是无可争议的品质。
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 /ˈɜːrsaɪn/

ursine

熊似的
Meaning
Relating to or resembling a bear.
Example
The man’s ursine strength amazed everyone.
那个人熊似的力量让所有人都吃惊。
B2 adjective /ʌnˈiːkwəl/

Unequal

不平等; 不公正;
Meaning
not the same in quantity, size, or value; not fair or just
Example
The distribution of wealth is unequal in many countries.
财富的分配在许多国家是不平等的。
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 adjective /ʌnˈsɜːrtən/

Uncertain

不确定
Meaning
not able to be relied on; not known or definite; not having reliable knowledge
Example
I am uncertain about my future career plans.
我对未来的职业规划感到不确定。
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。
C1 adjective /ʌnˈsɪvəlaɪzd/

Uncivilized

未开化的; 野蛮的;
Meaning
not developed in terms of civilization; lacking social organization and culture; barbarous
Example
The explorers encountered an uncivilized tribe deep in the Amazon rainforest.
探险者在亚马逊雨林深处遇到一个未开化的部落。
B1 adjective /ʌnˈfrɛndli/

unfriendly

不友好的
Meaning
not kind or welcoming; hostile or cold in behavior or attitude
Example
The shop owner seemed unfriendly to new customers.
店主对新顾客显得不友好。
C1 adjective /ʌnˈsɪvəl/

Uncivil

不文明的; 粗鲁的;
Meaning
not polite or courteous; rude and discourteous in behavior
Example
His uncivil remarks during the meeting offended everyone present.
他在会议上的不文明言论冒犯了在场的每一个人。
C2 noun /ˈʌŋɡwənt/

unguent

药膏
Meaning
A soothing or healing ointment applied to the skin.
Example
The doctor applied an unguent to heal the burn.
医生涂抹了药膏来治愈烧伤。
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 /ʌnˈnesəseri/

Unnecessary

不必要的；多余的
Meaning
not needed; not required; pointless
Example
The meeting was unnecessary since all decisions were already made.
会议是多余的，因为所有的决定已经做出。
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 verb /ʌpˈhoʊld/

uphold

维护
Meaning
to maintain or support a principle, law, or decision
Example
The judge promised to uphold justice at all costs.
法官承诺不惜一切代价维护正义。
B1 adjective /ʌnˈjuzd/

Unused

未使用的; 没有被使用
Meaning
not being used; not having been used before
Example
There are many unused rooms in this old mansion.
这个古老的豪宅里有许多未使用的房间。
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。
B2 adjective /ˌʌnkənˈvɛnʃənl/

unconventional

非传统的
Meaning
not based on or conforming to what is generally done or believed
Example
Her unconventional approach to teaching inspired her students to think creatively.
她非传统的教学方法激发了学生的创造性思维。
B1 adjective /juːˈnaɪtɪd/

United

联合的; 一致的; 团结的
Meaning
joined together for a common purpose; in agreement
Example
The team was united in their goal to win.
团队在他们的目标上达成了统一。
C1 adjective /ʌnˈsiːmli/

unseemly

不得体
Meaning
Not proper or appropriate in behavior or appearance; unbecoming.
Example
His unseemly remarks embarrassed everyone at the dinner table.
他不得体的言论让晚餐桌上的每个人都感到尴尬。
C1 adjective /ʌnˈkleɪmd/

Unclaimed

未认领的; 未要求的; 被遗弃或无主的
Meaning
not claimed by anyone; not demanded or requested; abandoned or ownerless
Example
The unclaimed luggage was stored in the airport's lost property department.
未认领的行李被存放在机场的失物招领处。
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。
C1 adjective /ʌnˈmaɪndfəl/

Unmindful

不留心的; 疏忽的;
Meaning
not paying attention; careless; heedless
Example
She was unmindful of the danger around her.
她没有注意到周围的危险。
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。
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。
C1 noun /ˈʌndərdɒɡ/

underdog

逆袭者
Meaning
a competitor thought to have little chance of winning; a weaker party in a contest
Example
The underdog team surprised everyone by winning the championship.
逆袭者队伍通过赢得锦标赛让所有人都惊讶。
C1 adjective /ʌnˈhoʊli/

Unholy

亵渎的; 罪恶的; 亵渎的
Meaning
wicked; sinful; profane
Example
The unholy alliance between the two companies caused public outrage.
这两家公司之间的不圣洁联盟引发了公众愤怒。
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 noun /ˌjuːnɪˈfɔːrməti/

Uniformity

一致性；统一性；相同状态
Meaning
the quality of being uniform; consistency or sameness
Example
The uniformity of the design created a pleasing visual effect.
设计的一致性创造了一个吸引人的视觉效果。
B1 adjective /ʌnˈlaɪkli/

Unlikely

不太可能; 不大可能
Meaning
not likely to happen; improbable
Example
It's unlikely to rain today with such clear skies.
今天晴空万里，几乎不可能下雨。
B2 adverb /ʌnˈplɛzəntli/

unpleasantly

令人不快地
Meaning
in a way that causes discomfort, annoyance, or displeasure; in an unfriendly or disagreeable manner
Example
The room was unpleasantly hot during the afternoon.
下午房间里热得令人不快。
C2 adjective /ˈʌŋk.tʃu.əs/

unctuous

阿谀奉承
Meaning
Excessively flattering or ingratiating; oily in texture.
Example
His unctuous tone made everyone uncomfortable.
他那种阿谀奉承的语气让每个人都感到不舒服。
C2 adverb /ʌnˈɜːrɪŋli/

unerringly

毫无错误
Meaning
Without making any mistakes; always accurate
Example
The archer aimed unerringly at the target.
弓箭手毫无错误地瞄准了目标。
B2 adjective /ˈʌl.tɪ.mət/

Ultimate

最终的; 极致的; 终极的
Meaning
being the best or most extreme example of its kind; final; last
Example
This is the ultimate test of your skills.
这是你技能的终极考验。
A1 adjective /ˈjuːs.fəl/

Useful

有用的; 实用的
Meaning
having a beneficial purpose; practical
Example
This tool is very useful for fixing problems.
这个工具对解决问题非常有用。
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。
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。
B2 adjective /ʌnˈhɜːrt/

unhurt

毫发无损
Meaning
Not injured or harmed.
Example
She walked away from the accident unhurt.
她在事故中毫发无损。
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。
B2 adjective /ʌnprɪˈpɛrd/

Unprepared

未准备好
Meaning
not ready or able to deal with something
Example
He was unprepared for the difficult exam.
他对困难的考试毫无准备。
C1 adjective /ʌnˈtɛnəbl/

untenable

无法维持
Meaning
not able to be maintained or defended against attack or objection
Example
The politician resigned when his position became untenable.
政治家在他的立场变得无法维持时辞职。
B1 adverb /ʌnˈjuːʒuəli/

unusually

异常地
Meaning
in a way that is not typical or expected; to an uncommon degree
Example
It was unusually cold for this time of year.
对一年中的这个时候来说，天气异常寒冷。
C1 adjective /ˌʌnprɪˈtɛnʃəs/

unpretentious

谦虚的
Meaning
modest; not attempting to impress others with appearance or importance
Example
She lives in an unpretentious home but is very happy.
她住在一个谦虚的家里，但非常快乐。
C1 noun ˌʌndərˈprɪvəlɪdʒd ɡruːps

underprivileged groups

贫困群体
Meaning
Groups of people who lack basic necessities or advantages that are available to other members of society.
Example
Underprivileged groups benefit from social initiatives.
贫困群体从社会倡议中受益。
B2 noun /ˈɜː.dʒən.si/

Urgency

紧急
Meaning
the quality of requiring immediate action or attention; pressing importance
Example
The urgency of the situation required immediate medical attention.
情况的紧急性要求立即的医疗关注。
C2 adjective /juːˈnɪsənənt/

unisonant

和谐的
Meaning
Sounding together or in harmony.
Example
The unisonant voices created a powerful effect.
和谐的声音创造了强大的效果。
B1 adjective /ˌʌnˈpeɪd/

Unpaid

未支付的; 无薪的
Meaning
not paid for; without payment or salary
Example
She worked as an unpaid intern for six months.
她作为一名无薪实习生工作了六个月。
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。
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。
C1 adjective /ʌnˈruːli/

Unruly

不守规矩的; 乱七八糟的;
Meaning
difficult to control or manage; disorderly and disruptive
Example
The unruly crowd refused to follow the safety instructions.
那群无法控制的人群拒绝遵循安全指令。
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。
C2 adjective /ʌnˈtɛmpərd/

untempered

失控的
Meaning
not moderated or softened; lacking proper balance or control
Example
The untempered anger of the crowd caused chaos.
人群的失控愤怒引发了混乱。
C1 adjective ʌnˈtʃɑːtɪd

uncharted

未标记
Meaning
Not mapped or surveyed; unknown or unexplored.
Example
The mission aimed to explore uncharted areas of the planet.
该任务旨在探索星球上未标记的区域。
C2 noun /ˈʌm.brə/

Umbra

完全的阴影，太阳黑子的黑暗中心
Meaning
the fully shaded inner region of a shadow cast by an opaque object; the dark center of a sunspot
Example
During the eclipse, we stood in the moon's umbra.
在日食期间，我们站在月亮的本影中。
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。
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。
C2 adjective /ʌnˈælɔɪd/

unalloyed

纯净
Meaning
Pure, complete, and not mixed with anything else.
Example
She felt unalloyed joy at the news of her success.
她听到成功的消息时感到纯粹的喜悦。
C1 adjective /ʌnˈtʌtʃəbəl/

Untouchable

不可触碰的; 无法批评或攻击
Meaning
not able to be touched or affected; beyond criticism or attack
Example
The CEO seemed untouchable despite the scandal.
即使有丑闻，首席执行官似乎仍然是不可触碰的。
B2 adjective /ʌnfəˈmɪl.jər/

Unfamiliar

不熟悉的; 陌生的
Meaning
not known or recognized; strange
Example
The city was unfamiliar to me since I had never been there before.
这座城市对我来说很陌生，因为我以前从未去过那里。
C1 verb /ˈʌndərkʌt/

undercut

Meaning
to sell at a lower price than a competitor; to weaken or undermine something
Example
The company tried to undercut its rivals by offering lower prices.
C2 noun /juːˌtɪlɪˈtɛəriənɪzəm/

utilitarianism

功利主义
Meaning
The ethical theory that actions are right if they are useful or for the benefit of the majority.
Example
Utilitarianism suggests that we should act to maximize overall happiness.
功利主义认为我们应该采取行动，以最大化整体幸福。
B2 adjective /ˌʌn.əkˈsep.tə.bəl/

Unacceptable

不可接受
Meaning
not satisfactory or allowable; not acceptable
Example
The quality of work was completely unacceptable.
工作质量完全不可接受。
B2 verb /ʌnˈveɪl/

unveil

揭示
Meaning
to reveal or disclose something, especially in a formal manner
Example
The company will unveil a new product next week.
公司将在下周揭示一款新产品。
B2 adjective /ʌnhaɪˈdʒiːnɪk/

Unhygienic

不卫生的；缺乏适当的卫生
Meaning
not clean; lacking proper sanitation
Example
The restaurant was closed due to unhygienic conditions in the kitchen.
由于厨房不卫生的条件，餐厅被关闭。
C1 adjective /ˌʌnkɒnstɪˈtuːʃənəl/

Unconstitutional

违宪的
Meaning
not in accordance with a political constitution; violating constitutional principles
Example
The court declared the new law unconstitutional.
法院宣布这项新法律违宪。
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。
C2 noun /ˈʌn.dɚˌstɔː.ri/

understory

下层植被
Meaning
The layer of vegetation beneath the main canopy of a forest.
Example
The understory of a rainforest is home to small mammals and insects.
雨林的下层植被是小型哺乳动物和昆虫的家园。
B2 adjective /ʌnˈriːdəbl/

unreadable

难以辨认的
Meaning
not able to be read or understood clearly; illegible
Example
The doctor’s handwriting was completely unreadable.
医生的字迹完全难以辨认。
A2 noun /ˈjuːnɪt/

unit

单元
Meaning
an individual thing or person regarded as a single and complete entity
Example
Each unit in the production line is carefully tested.
生产线上的每个单元都经过仔细测试。
C1 adjective /ʌnˈskeɪðd/

unscathed

毫发无损
Meaning
Without suffering any injury, damage, or harm.
Example
She escaped from the accident unscathed.
她毫发无损地逃离了事故。
B2 adjective /ˌjuːnɪˈvɜːrsəl/

Universal

普遍的
Meaning
applicable to all cases; existing everywhere
Example
Music is a universal language that everyone understands.
音乐是一种普遍的语言，人人都能理解。
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。
B2 adjective /ʌnˈfɪt/

Unfit

不适合; 不适当;
Meaning
not in good physical condition; unsuitable or inappropriate
Example
He was declared unfit for military service due to his poor health.
由于健康状况差，他被宣判不适合军事服务。
A1 noun /ˈʌŋkəl/

uncle

叔叔/舅舅
Meaning
the brother of one's father or mother
Example
My uncle is visiting us next week.
我的叔叔下周会来看我们。
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。
A2 adjective /ˈjuːs.ləs/

Useless

无用
Meaning
having no beneficial purpose; not useful
Example
This broken computer is completely useless.
这个坏掉的电脑完全是无用的。
C1 adjective /ʌnˈvaɪəbl/

unviable

不可行的
Meaning
Not capable of working successfully; not feasible or practical.
Example
The project was deemed unviable due to high costs.
由于高昂的成本，该项目被认为不可行。
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。
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。
A2 adjective /ˈjuːʒəl/

usual

常见
Meaning
habitually or typically occurring or done
Example
It’s our usual meeting spot.
这是我们常见的会议地点。
B2 adjective /ʌnˈskɪld/

Unskilled

无技能的; 无技术的工人
Meaning
lacking technical training or ability; not requiring special skills
Example
Many unskilled workers are looking for training opportunities.
许多没有技能的工人正在寻找培训机会。
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 adjective /ˌʌndɪˈsaɪdɪd/

Undecided

未决定的; 不确定的
Meaning
not having made a decision; uncertain
Example
She was undecided about which college to attend.
她对于选择哪个大学感到未决定。
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 adjective /juːˈbɪkwɪtəs/

ubiquitous

无处不在
Meaning
Existing or being everywhere at the same time.
Example
Social media has become ubiquitous among young people.
社交媒体在年轻人中变得无处不在。
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。
B2 verb /ʌnˈkʌvə(r)/

uncover

揭示
Meaning
to reveal something that was hidden or secret
Example
The investigation uncovered new evidence.
调查揭示了新的证据。
C2 verb /ʌpˈhiːv/

upheave

抬起
Meaning
to lift or raise something forcefully; to cause to rise suddenly
Example
The workers had to upheave the heavy stone to clear the path.
工人们不得不抬起重石来清理道路。
C1 adjective /ˌʌnˈpɑr.də.nə.bəl/

Unpardonable

不可宽恕的
Meaning
too bad to be forgiven; inexcusable
Example
His betrayal of trust was an unpardonable offense.
他的背叛是不可原谅的罪行。
B2 adjective /ʌnˈiːzi/

Uneasy

不安的; 焦虑的; 不舒服的
Meaning
worried; anxious; uncomfortable; restless
Example
She felt uneasy about walking alone at night.
她在夜晚独自行走时感到不安。
C1 adjective /ʌnˈweɪ.vər.ɪŋ/

unwavering

坚定
Meaning
Steady or resolute; not wavering.
Example
He showed unwavering dedication to his goal.
他展示了对目标的坚定承诺。
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。
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。
B2 adverb /ˈʌltəmətli/

ultimately

最终
Meaning
in the end, after everything else
Example
Ultimately, we decided to go ahead with the project.
最终，我们决定继续推进该项目。
A2 noun /ˈʌndərwɛr/

Under wear

内衣
Meaning
clothing worn under other clothes, next to the skin
Example
She bought new underwear from the department store.
她在百货商店买了新的内衣。
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。
B2 adjective /ʌnˈprɒf.ɪ.tə.bl̩/

Unprofitable

无利可图
Meaning
not yielding profit or gain; not producing financial benefit
Example
The unprofitable business was forced to close down after three years.
这个无利可图的生意在三年后被迫关闭。
C1 verb /ʌnˈsɛtl/

unsettle

扰乱
Meaning
To disturb or make someone feel anxious or uneasy.
Example
The sudden news unsettled the entire community.
突如其来的消息让整个社区感到不安。
B2 noun /ʌnəˈbɪləti/

unability

无能
Meaning
the state of being unable to do something; incapacity
Example
His unability to solve the problem caused delays in the project.
他解决问题的无能导致了项目的延误。
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 /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。
C1 adjective /ʌnˈsɜːrvɪsəbəl/

Unserviceable

无法使用的; 有缺陷的
Meaning
not in working order; unable to be used; defective
Example
The old computer became unserviceable after the system crash.
那台旧电脑在系统崩溃后变得无法使用。
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.
B1 adjective /ʌnˈlaɪk/

Unlike

不同的; 不相似的
Meaning
different from; not similar to
Example
Unlike his brother, he prefers quiet activities.
与他哥哥不同，他喜欢安静的活动。
B2 adjective /ʌnˈtʃeɪndʒəbəl/

Unchangeable

不可改变的; 固定的;
Meaning
not able to be changed or altered; fixed and permanent
Example
The laws of physics are unchangeable principles that govern the universe.
物理法则是不变的原则，支配着宇宙。
A1 adjective /juːzd/

used

二手
Meaning
having already been used
Example
This is a used car.
这是一辆二手车。
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 verb /ˌʌndərˈɡoʊ/

undergo

经历
Meaning
to go through something, especially something unpleasant or difficult
Example
She had to undergo surgery to recover.
她不得不接受手术以恢复。
C1 noun /ˌʌnbɪˈliːf/

Unbelief

不信
Meaning
lack of religious belief; skepticism or doubt
Example
His unbelief in the supernatural made him a skeptic.
他对超自然的怀疑使他成为了一个怀疑者。
B2 adjective /ʌnˈwɪl.ɪŋ/

Unwilling

不愿意的; 不情愿的;
Meaning
not ready to do something; reluctant; not wanting to do
Example
He was unwilling to share his secret with anyone.
他不愿意与任何人分享他的秘密。
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 /ˌʌnfɔːrˈsiːn/

unforeseen

Meaning
Not anticipated or predicted; unexpected.
Example
The project faced unforeseen challenges that delayed its completion.
B2 noun /ˈjuː.sɪdʒ/

Usage

使用
Meaning
the action of using something; the way in which words are used in a language
Example
The dictionary explains the correct usage of difficult words.
词典解释了难词的正确用法。
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 verb /ˈʌndjʊleɪt/

undulate

波动
Meaning
To move with a smooth, wave-like motion.
Example
The snake undulated across the sand.
蛇在沙滩上蜿蜒前行。
B2 adjective /ˈʌt.ɚ/

Utter

完全的; 绝对的; 全部的
Meaning
complete; absolute; total
Example
The movie was an utter disaster at the box office.
这部电影在票房上完全失败了。