undercut
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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.
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。
C1 noun /ˈʌlsər/

ulcer

Meaning
a sore on the skin or a mucous membrane that does not heal easily
Example
The doctor prescribed medicine to treat the stomach ulcer.
B2 adjective /ʌnˌkənˈdɪʃ.ən.əl/

Unconditional

无条件的
Meaning
not subject to any conditions; complete and absolute
Example
She offered her unconditional support to her friend in need.
她在朋友需要时提供了无条件的支持。
B1 adjective /ˈɜːrbən/

urban

城市的
Meaning
related to, characteristic of, or situated in a city or town
Example
Urban areas often have higher population density than rural areas.
城市地区通常比乡村地区有更高的人口密度。
C2 adjective /ʌnəˈpiːzd/

unappeased

不平息的
Meaning
Not satisfied or calmed; still feeling discontent or anger
Example
Despite the apology, she remained unappeased.
尽管道歉，她仍然不平息的。
B1 adjective /ʌnˈklɪər/

unclear

不清楚
Meaning
not easy to understand; vague or ambiguous
Example
The instructions were unclear, so I asked for clarification.
说明不清楚，所以我要求澄清。
C1 adjective /ˌʌnbɪˈliːvɪŋ/

unbelieving

不相信的
Meaning
Not willing or able to believe; skeptical or doubtful
Example
She gave him an unbelieving look when he claimed to have met a celebrity.
当他声称见过一位名人时，她给了他一个不相信的眼神。
B2 adjective /ˌʌnəˈfɪʃ.əl/

Unofficial

非官方的
Meaning
not officially authorized or confirmed; informal
Example
The unofficial results showed a close race.
非官方的结果显示出一场激烈的比赛。
C1 noun /ˌʌnriˈælɪti/

unreality

非现实
Meaning
the state or quality of being unreal; lack of reality or truth
Example
The dreamlike setting gave the story a sense of unreality.
这种梦幻的场景让故事充满了非现实感。
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。
C1 verb /ʌnˈmɑːsk/

unmask

揭露；暴露真相
Meaning
to remove a mask or covering; to reveal the true identity, nature, or intentions of someone or something
Example
The investigation helped unmask the real culprit behind the crime.
调查帮助揭露了犯罪背后的真正罪犯。
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。
A1 verb /ˌʌndərˈstænd/

understand

理解
Meaning
to know the meaning of something; to comprehend
Example
Do you understand the instructions?
你理解这些指示吗?
B2 adjective /ˌʌnəˈweər/

Unaware

无意识的; 不知道的; 没有意识
Meaning
not knowing or realizing; having no knowledge of something
Example
She was completely unaware of the danger.
她完全没有意识到危险。
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。
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。
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。
C2 adjective /ˌʌnɪkˈsɛpʃənəbl/

unexceptionable

无可指摘
Meaning
Not open to objection; acceptable and unobjectionable
Example
His behavior was unexceptionable throughout the event.
他的行为在整个事件中都是无可指摘的。
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。
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。
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。
C1 noun /ˈjuːnɪsən/

unison

齐声
Meaning
Simultaneous performance or utterance of action or speech.
Example
The choir sang in unison.
合唱团齐声唱歌。
C2 adjective /ˈʌndjʊleɪtɪŋ/

undulating

波动的
Meaning
Having a smoothly rising and falling form or motion like waves.
Example
We drove through undulating hills.
我们驱车穿过起伏的山丘。
C2 adjective /ɜːrˈbeɪn/

urbane

都市的
Meaning
showing polished manners, refinement, and sophistication
Example
He was an urbane gentleman who charmed everyone at the party.
他是一个都市绅士，在派对上迷住了所有人。
C1 adjective ʌnˈwɔːr.rən.tɪd

unwarranted

不合理的
Meaning
Not justified or necessary; without good reason.
Example
His anger toward the staff was completely unwarranted.
他对员工的愤怒是完全不合理的。
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 noun ˌjuːtɪlaɪˈzeɪʃən

utilization

利用
Meaning
The action of making practical and effective use of something.
Example
Increased plastic utilization calls for better waste management.
塑料的使用增加要求更好的废物管理。
C1 adjective /ˌʌnəbˈtruːsɪv/

unobtrusive

不引人注目
Meaning
not attracting attention; blending in without causing notice
Example
The security cameras are designed to be unobtrusive.
安全摄像头被设计成不引人注目。
C1 adjective ʌnˈjiːl.dɪŋ

unyielding

坚定或坚韧
Meaning
Not easily broken or giving in to pressure.
Example
Her unyielding determination helped her overcome all challenges.
她坚定的决心帮助她克服了所有的挑战。
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。
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。
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.
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。
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 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。
B2 adjective /ˌʌnˈkɔːrdɪneɪtɪd/

uncoordinated

不协调; 笨拙
Meaning
lacking coordination, not well-organized or clumsy in movement
Example
His movements were uncoordinated, making him prone to accidents.
他的动作不协调，使他容易发生意外。
C2 adjective /ʌkˈsɔːriəs/

uxorious

过度宠爱妻子
Meaning
excessively fond of or submissive to one's wife
Example
He was so uxorious that he agreed with everything his wife said.
他是如此的宠爱妻子，以至于同意了妻子说的每一件事。
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。
B2 adjective /ʌnˈraɪp/

Unripe

未成熟的
Meaning
not fully developed or matured; not ready to be eaten
Example
The unripe bananas will turn yellow in a few days.
未成熟的香蕉几天后会变黄。
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。
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。
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。
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。
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。
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。
B2 adjective /ʌnˈhɛlpfəl/

unhelpful

没有帮助的
Meaning
not providing help or support; making a situation harder rather than easier
Example
His unhelpful attitude slowed down the entire project.
他没有帮助的态度拖慢了整个项目。
B1 adjective /ˌʌndərˈstændəbl/

understandable

可以理解的
Meaning
Able to be understood; reasonable or justifiable.
Example
Her reaction was understandable given the situation.
考虑到情况，她的反应是可以理解的。
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 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。
C1 adjective /ʌnˈseɪvəri/

unsavory

令人不快
Meaning
Disagreeable, unpleasant, or morally offensive.
Example
The politician was linked to an unsavory scandal.
那位政治家与一宗令人不快的丑闻有关。
B2 adjective /ˌʌnprɪˈdɪktəbəl/

unpredictable

不可预测的
Meaning
not able to be predicted; changing suddenly and unexpectedly
Example
The weather in this region is highly unpredictable.
这个地区的天气非常不可预测。
B2 adverb /ʌnˈnesəserəli/

Unnecessarily

不必要地
Meaning
to a greater extent than is needed; without necessity
Example
Don't worry unnecessarily about the exam.
不要为考试不必要地担心。
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。
B1 verb /juˈnaɪt/

unite

联合
Meaning
to join together or combine; to bring people or things together
Example
The crisis helped unite the community.
危机帮助团结了社区。
B2 adverb /ʌnˈkaɪndli/

unkindly

残忍地
Meaning
in a cruel, harsh, or unsympathetic manner
Example
She spoke unkindly about her colleague during the meeting.
她在会议期间残忍地谈论了她的同事。
C1 adjective /ʌnˈduː/

Undue

过度的; 不适当的; 超过必要或适当的
Meaning
excessive; inappropriate; more than is necessary or proper
Example
The teacher complained about undue pressure from parents.
老师抱怨家长施加的过度压力。
B2 adjective /ʌnˈhɜːd/

Unheard

未听到的; 未知的
Meaning
not heard or listened to; not given a hearing; unknown or unfamiliar
Example
His complaints went unheard by the management.
他的投诉没有被管理层听到。
B2 adverb /ʌnˈwɪlɪŋli/

unwillingly

不情愿地
Meaning
in a way that shows reluctance or lack of desire; not willingly
Example
She unwillingly agreed to attend the meeting.
她不情愿地同意参加会议。
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。
C1 adjective /ʌnˈsəʊʃəl/

unsocial

不合群的
Meaning
not enjoying the company of others; avoiding social interaction; contrary to social norms
Example
He prefers unsocial hours so he can work alone without interruptions.
他更喜欢不合群的工作时间来独自工作。
B1 noun /ʌnˈhæp.i.nəs/

unhappiness

不快乐
Meaning
the state of being unhappy; sadness or dissatisfaction
Example
Her constant unhappiness affected everyone around her.
她持续的不快乐影响了周围的每一个人。
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 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。
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。
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 /ʌnˈkwaɪ.ət/

Unquiet

不安的; 焦虑的; 激动的
Meaning
restless; unable to remain still or quiet; anxious or troubled
Example
She spent an unquiet night worrying about the exam results.
她度过了一个不安的夜晚，担心考试结果。
B2 adjective /ʌnˈsiːn/

Unseen

看不见的；未曾看到或注意到的
Meaning
not previously seen or noticed; invisible; hidden
Example
The unseen forces of nature can be very powerful.
自然界的看不见的力量可能非常强大。
B2 adjective /ʌnˈfeɪθ.fəl/

Unfaithful

不忠诚
Meaning
not loyal or true to a spouse, partner, or commitment
Example
He was unfaithful to his wife for many years.
他对妻子不忠诚多年。
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 /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 /ʌnˈflæpəbəl/

unflappable

冷静沉着
Meaning
calm and composed, especially in difficult situations
Example
Despite the crisis, he remained unflappable and confident.
尽管面临危机，他依然保持冷静沉着，充满自信。
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。
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 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。
A2 adjective /ʌnˈtaɪdi/

Untidy

凌乱的; 无序的;
Meaning
not neat or orderly; messy and disorganized
Example
Her untidy room was filled with clothes scattered everywhere.
她凌乱的房间充满了四处散落的衣服。
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。
C2 verb /ʌnˈjoʊk/

unyoke

解开
Meaning
To release from a yoke or to free from restraint or obligation.
Example
The farmer unyoked the oxen after a long day of work.
农民在长时间工作后解开了牛的套索。
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。
B1 adjective /ˌʌnbɪˈliːvəbəl/

Unbelievable

难以置信
Meaning
impossible to believe; extremely surprising or remarkable
Example
The magician's performance was absolutely unbelievable.
魔术师的表演简直令人难以置信。
B2 adjective /ˈjuː.nɪ.faɪd/

unified

统一
Meaning
Made into a whole or joined together.
Example
A unified approach fosters better outcomes.
统一的方法促进了更好的结果。
B2 adjective /ʌnˈkɒmən/

uncommon

不常见
Meaning
rare, unusual, or remarkable
Example
It is uncommon to see snow in this region.
在这个地区看到雪是不常见的。
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。
A2 adjective /ʌnˈhel.θi/

Unhealthy

不健康的; 有害的
Meaning
harmful to health; not in good health; detrimental to well-being
Example
Eating too much fast food is unhealthy for your body.
吃太多快餐对你的身体不健康。
A1 verb /juːz/

use

使用
Meaning
to employ something for a purpose; to take advantage of
Example
I use my computer for work and entertainment.
我用我的计算机来工作和娱乐。
B1 adjective /ʌnˈwɒn.tɪd/

Unwanted

不受欢迎的
Meaning
not desired or welcome; not wanted
Example
He felt like an unwanted guest at the meeting.
他在会议上觉得自己像个不受欢迎的客人。
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。
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。
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。
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。
B1 adjective /ˌʌnɪmˈpɔːrtənt/

unimportant

不重要的
Meaning
not having much value, significance, or influence
Example
The detail seemed unimportant compared to the main issue.
与主要问题相比，这个细节显得不重要。
B2 adjective /ʌnˈkwɒl.ɪ.faɪd/

Unqualified

不合格的; 无资格的;
Meaning
not having the necessary skills or qualifications; complete or absolute
Example
He was unqualified for the engineering position due to lack of experience.
他因缺乏经验而不适合这个工程职位。
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。
B2 adverb /ʌnˈkɒnʃəsli/

unconsciously

无意识地
Meaning
without being aware of one's actions or surroundings
Example
She unconsciously tapped her foot to the rhythm of the music.
她无意识地跟着音乐的节奏轻轻跺脚。
B2 adverb /ˈʌt.ə.li/

Utterly

完全地; 绝对地; 完整地
Meaning
completely; absolutely; totally
Example
The movie was utterly boring and I fell asleep.
电影完全无聊，我睡着了。
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。
B1 adjective /ʌnɪmˈplɔɪd/

Unemployed

失业
Meaning
without a job; not having paid work
Example
He has been unemployed for six months now.
他已经失业六个月了。
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 /ʌnˈbraɪdld/

unbridled

无法控制的
Meaning
Uncontrolled and unrestrained.
Example
The protesters showed unbridled enthusiasm for change.
抗议者展示了对改变的无法抑制的热情。
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。
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。
C1 noun /juːˈtoʊpiə/

utopia

乌托邦
Meaning
An imagined perfect society or place where everything is ideal.
Example
Many philosophers dreamed of creating a utopia for humanity.
许多哲学家梦想着为人类创造一个乌托邦。
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 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。
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 /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。
B1 adjective /ʌnˈtru/

Untrue

错误的; 不正确的
Meaning
not true; false; incorrect
Example
His statement about the incident was completely untrue.
他关于事件的陈述完全是错误的。
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 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。
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。
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。
C2 noun /ˌjuːzɜːrˈpeɪʃən/

usurpation

篡夺
Meaning
The act of taking someone's power or property illegally or by force.
Example
The general's usurpation of the presidency led to political unrest.
将军对总统职位的篡夺导致了政治动荡。
B2 adjective /ʌnˈdʒʌst/

Unjust

不公正的; 错误的
Meaning
not fair or right; morally wrong
Example
The punishment was unjust for such a minor offense.
这个惩罚对于如此轻微的罪行来说是不公正的。
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。
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。
B1 adjective /ʌnˈseɪf/

Unsafe

不安全; 危险的;
Meaning
involving or causing danger or risk; not protected from harm
Example
It is unsafe to walk alone in this neighborhood at night.
晚上在这个社区独自行走是不安全的。
B2 adjective /ʌnˈfeɪ.vər.ə.bəl/

Unfavourable

不利的; 逆境的
Meaning
not helpful or advantageous; adverse
Example
The weather conditions were unfavourable for our outdoor event.
恶劣的天气条件不利于我们的户外活动。
C1 verb /ʌnˈnɜːrv/

unnerve

失去信心
Meaning
to make someone lose confidence, courage, or composure
Example
The hostile questions began to unnerve the witness.
敌对问题开始让证人感到不安。
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 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。
B2 verb ˈjuːnɪfaɪ

unify

统一
Meaning
To make or become united, uniform, or whole; to bring together into a single unit.
Example
Adolescents unify with peers for social acceptance.
青少年为了社会接纳与同伴统一。