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B1 adjective /ʌnˈnoʊn/

Unknown

未知
Meaning
not known or identified; unfamiliar
Example
The author of this letter remains unknown.
这封信的作者仍然未知。
C2 noun /ˈʌp.wel.ɪŋ/

upwelling

上升流
Meaning
An oceanographic phenomenon that involves wind-driven motion of dense, cooler, and nutrient-rich water towards the ocean surface.
Example
Upwelling brings nutrients to the ocean surface.
上升流将营养物质带到海洋表面。
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。
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。
B2 adjective /ˌʌnɪˈmædʒənəbəl/

Unimaginable

难以想象的
Meaning
impossible to conceive; beyond imagination
Example
The scale of destruction was unimaginable until we saw it firsthand.
毁灭的规模是难以想象的，直到我们亲眼看到。
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。
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。
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。
C1 adjective /ˌʌnəˈfɛktɪd/

unaffected

不受影响的, 自然的
Meaning
Not influenced or touched by something; genuine and natural.
Example
He remained unaffected by the criticism and kept working hard.
他对批评毫不受影响，继续努力工作。
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。
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。
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。
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。
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。
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 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 /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 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 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。
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.
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 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 /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。
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 /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。
C1 verb /ˌʌn.dəˈtʃɑːrdʒ/

undercharge

收取较少费用
Meaning
To charge less than the correct or fair amount.
Example
The shopkeeper accidentally undercharged me for the groceries.
店主不小心少收了我购买食品的钱。
C2 noun /ˌjuːnɪˈtɛəriən/

unitarian

一神论者
Meaning
A person who believes that God exists as one entity rather than as a Trinity; a member of a religious denomination that emphasizes individual freedom of belief.
Example
The Unitarian church is known for its inclusive and open-minded approach.
一神论教会以其包容和开放的思想方式而闻名。
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。
B2 noun /juːˈtɪl.ə.ti/

Utility

效用; 益处; 公共服务
Meaning
the state of being useful, profitable, or beneficial; a public service
Example
The utility of solar panels increases with rising electricity costs.
随着电费上涨，太阳能板的效用也在增加。
B2 adjective /ʌnˈendɪŋ/

Unending

无尽的
Meaning
continuing forever; without end
Example
The unending rain made the day feel gloomy.
无尽的雨让这一天显得阴沉。
B2 adjective /ʌnˈbiːtən/

Unbeaten

不败的; 未被击败的
Meaning
not defeated; having never lost; undefeated
Example
The team remains unbeaten this season.
这个团队本赛季保持不败。
B2 noun /ˌʌndəˈɡrædʒuət/

undergraduate

本科生
Meaning
a student who has not yet earned a bachelor's degree
Example
She is an undergraduate studying computer science.
她是一个学习计算机科学的本科生。
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。
C1 adjective /ʌnˈɡɑː.dɪd/

Unguarded

不设防的
Meaning
not protected or defended; careless about revealing private thoughts or information
Example
In an unguarded moment, she revealed her true feelings about the project.
在一个不设防的时刻，她揭示了她对这个项目的真实感受。
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 /ʌnˈtaɪərɪŋ/

Untiring

不知疲倦的; 坚持不懈的; 永不止步的
Meaning
continuing without stopping; persistent; tireless
Example
Her untiring efforts finally led to success.
她的不知疲倦的努力最终带来了成功。
C1 adjective /ʌnˈtʃælɪndʒd/

Unchallenged

无可争议的; 被接受的没有反对; 没有对手
Meaning
not disputed or questioned; accepted without opposition; having no rival
Example
He remained the unchallenged champion for five years.
他五年保持不败的冠军。
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 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 ʌnˈmætʃt

unmatched

无与伦比
Meaning
Not equaled or rivaled by any other; without equal.
Example
The freedom fighters showed unmatched bravery.
自由战士们展示了无与伦比的勇气。
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 /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。
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。
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。
A2 conjunction /ʌnˈlɛs/

unless

除非
Meaning
except if
Example
We won't go unless it stops raining.
除非雨停了，否则我们不去。
B1 verb /ʌnˈlɒk/

unlock

解锁
Meaning
to open something that is locked; to make something accessible or available
Example
She used the key to unlock the door.
她用钥匙解锁了门。
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 /ʌnˈmɒdɪfaɪd/

unmodified

未修改的
Meaning
not changed from its original form or state
Example
The data was used in its unmodified form for analysis.
这些数据以未修改的形式用于分析。
C2 adjective /ˌʌnprəˈpɪʃəs/

unpropitious

不利
Meaning
Not giving or indicating a good chance of success; unfavorable.
Example
The team began their journey under unpropitious weather conditions.
团队在不利的天气条件下开始了他们的旅程。
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。
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。
B1 adjective /ʌnˈeɪ.bəl/

Unable

无法
Meaning
lacking the power, skill, or means to do something
Example
He was unable to attend the meeting.
他无法参加会议。
C2 adjective /ˌʌltrəˈmɒnteɪn/

ultramontane

教皇支持者
Meaning
beyond the mountains, especially referring to support for the Pope over local church authority
Example
The debate highlighted the ultramontane position in church politics.
辩论突出了教会政治中超山的立场。
C2 adjective /ʌnˈfeɪnd/

unfeigned

真诚
Meaning
genuine; not pretended or insincere
Example
She expressed unfeigned joy at her friend's success.
她在朋友的成功上表达了真诚的喜悦。
C2 adjective /ʌnˈwiːldi/

unwieldy

笨重
Meaning
Difficult to carry or move because of its size, shape, or weight.
Example
The box was too unwieldy to carry up the stairs.
这个盒子太笨重了，无法把它提上楼梯。
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。
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。
C2 noun /ˈʌmbrɪdʒ/

umbrage

冒犯，愤怒
Meaning
A feeling of resentment or offense.
Example
She took umbrage at his rude remark.
她对他的粗鲁言论感到愤怒。
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 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。
C1 adjective /ʌlˈtɪəriər/

ulterior

隐藏的动机
Meaning
hidden or secret, often with a selfish motive
Example
He invited her with an ulterior motive.
他带着隐藏的动机邀请了她。
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 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。
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。
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。
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 /ʌnˈθɪŋkɪŋ/

unthinking

欠考虑的
Meaning
done without careful thought; automatic or thoughtless
Example
His unthinking remark hurt her feelings.
他欠考虑的评论伤害了她的感情。
C1 verb /ʌnˈroʊl/

unroll

展开
Meaning
to open something that is rolled up; to spread out gradually
Example
She unrolled the map on the table to find the route.
她把地图在桌子上展开来寻找路线。
B1 noun /ˈjuːs.fəl.nəs/

Usefulness

有用性
Meaning
the quality of being useful; practical value or helpfulness
Example
The usefulness of this tool became apparent during the project.
这个工具的有用性在项目过程中变得显而易见。
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。
A2 adjective /ˈʌɡ.li/

Ugly

丑陋的; 可憎的; 可怕的
Meaning
unpleasant or repulsive in appearance; morally reprehensible
Example
The old building looked ugly after years of neglect.
这座老建筑在多年疏忽之后看起来很丑。
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。
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。
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。
B2 adjective /ʌnəˈfreɪd/

unafraid

无畏
Meaning
Not feeling fear; brave or courageous
Example
She walked into the dark room, unafraid of what might be inside.
她走进黑暗的房间，无畏里面可能有什么。
C1 adjective /ʌnˈspiːkəbl/

unspeakable

难以形容
Meaning
too bad or shocking to be expressed in words
Example
The survivors endured unspeakable horrors during the war.
幸存者在战争中忍受了难以形容的恐怖。
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。
B1 adjective /juːˈniːk/

Unique

独特的; 唯一的; 稀有的
Meaning
being the only one of its kind; unlike anything else
Example
Every snowflake is unique in its pattern.
每一片雪花在它的图案中都是独一无二的。
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 /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 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 noun /ˈʌndərkləʊðz/

underclothes

内衣
Meaning
Clothing worn beneath outer clothes, such as underwear or lingerie
Example
He folded his underclothes neatly before packing them.
他在打包前把内衣叠得整整齐齐。
B2 adjective /ʌnˈwɜːrði/

Unworthy

不配; 没有价值
Meaning
not deserving respect or attention; lacking worth or merit
Example
He felt unworthy of such praise and recognition.
他觉得自己不配得到这样的赞扬和认可。
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。
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 /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 noun /ɜːrˈbænɪti/

urbanity

都市气质
Meaning
refined courtesy, elegance, and sophistication in manner
Example
Her urbanity made her popular among diplomats and leaders.
她的都市气质让她在外交官和领导人中非常受欢迎。
B1 adjective /ʌnˈwel/

Unwell

不舒服; 生病
Meaning
not in good health; feeling sick or ill
Example
She has been feeling unwell since yesterday.
她从昨天开始感到不舒服。
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。
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。
B2 adjective /ˌʌnrɪˈzɒlvd/

unresolved

未解决的
Meaning
not solved or settled; remaining undecided or unclear
Example
The dispute remains unresolved despite several meetings.
尽管开了几次会议，这个争议仍未解决。
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。
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 /ˌʌnəˈsweɪdʒd/

unassuaged

未缓解
Meaning
Not made less intense or relieved; unrelieved.
Example
His grief remained unassuaged despite the passage of time.
他的痛苦尽管时间流逝依然未缓解。
C2 adjective /ʌnˈflɛdʒd/

unfledged

未经训练的
Meaning
Inexperienced, immature, or not fully developed.
Example
The unfledged writer struggled to complete his first novel.
这个未经训练的作家难以完成他的第一本小说。
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。
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 /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。
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。
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 /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 + 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。
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。
B2 adverb /ʌnˈsɜːrtənli/

uncertainly

不确定地
Meaning
in a way that shows doubt or lack of certainty
Example
She glanced uncertainly at the complicated instructions.
她不确定地看着复杂的说明。
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。
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。
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。
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 /ˈʌpər/

upper

上层
Meaning
higher in position or rank
Example
The upper floor of the building is under renovation.
建筑物的上层正在翻修。
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。
B2 adjective /ʌnˈɡreɪt.fəl/

Ungrateful

忘恩负义
Meaning
not feeling or showing thanks for something done or given; not appreciating kindness
Example
She felt he was ungrateful for all the help she had given him.
她觉得他对她给予的所有帮助都忘恩负义。
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。
B1 adjective /ˈɜːrdʒənt/

Urgent

紧急
Meaning
requiring immediate action or attention; pressing
Example
The patient needs urgent medical attention.
病人需要紧急医疗照顾。
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 verb /ʌpˈdeɪt/

update

更新
Meaning
to make something more modern or current; to provide new information
Example
Please update your software regularly.
请定期更新您的软件。
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。
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 /ʌnˈsuːtəbl/

Unsuitable

不适合; 不合适
Meaning
not fitting or appropriate for a particular purpose or situation
Example
This formal dress is unsuitable for a casual beach party.
这件正式的衣服不适合参加随意的海滩派对。
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。
A2 adjective /ʌnˈhæp.i/

Unhappy

不快乐; 难过
Meaning
not happy; feeling sad or displeased; unfortunate or undesirable
Example
He was unhappy with the results of his exam.
他对考试结果感到不满。
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。