unwitting
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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。
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。
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。
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。
C2 adjective /ʌnˈstɪntɪŋ/

unstinting

慷慨的
Meaning
given generously without holding back
Example
She received unstinting support from her family.
她从家人那里得到了慷慨的支持。
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。
A1 interjection /ʌ/

uh

呃
Meaning
a sound people make when they hesitate or are unsure what to say next.
Example
Uh, I’m not sure if that’s the right answer.
呃，我不确定这是不是正确的答案。
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。
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。
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 /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。
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 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.
C1 adjective /ʌnˈdɔːntɪd/

Undaunted

无畏的; 勇敢的; 不屈的;
Meaning
not intimidated or discouraged by difficulty, danger, or disappointment
Example
Despite the setbacks, she remained undaunted in pursuing her goals.
尽管遇到挫折，她在追求目标时依然无畏。
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 /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 /ʌnˈkɒn.ʃəs/

Unconscious

昏迷; 无意识
Meaning
not awake and aware of one's surroundings; done or existing without one realizing
Example
The patient was unconscious for several hours after the surgery.
病人在手术后昏迷了几个小时。
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。
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 adjective ˌʌn.əˈseɪ.lə.bəl

unassailable

不可攻破
Meaning
Unable to be attacked, questioned, or defeated.
Example
An unassailable position ensures dominance.
不可攻破的位置确保主导地位。
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 /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 /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。
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 /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。
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。
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。
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。
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。
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 adjective /ˌʌndɪˈstɜːrbd/

Undisturbed

未打扰
Meaning
not interrupted or interfered with; calm and peaceful
Example
She slept undisturbed for eight hours.
她睡了八个小时没有打扰。
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。
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 verb /ʌnˈɜːθ/

unearth

发掘
Meaning
To dig up from the ground or to discover something hidden.
Example
Archaeologists unearthed ancient artifacts at the site.
考古学家在遗址发掘了古代文物。
C1 adjective /ˌʌnəˈsjuːmɪŋ/

unassuming

谦虚
Meaning
Not pretentious or arrogant; modest.
Example
Despite his success, he remained unassuming and humble.
尽管他取得了成功，他仍然谦虚和谦逊。
C1 adjective ʌnɪnˈhæbɪtəbəl

uninhabitable

不可居住
Meaning
Not suitable or safe for people to live in.
Example
Rapid urbanization can make cities uninhabitable.
快速城市化可能使城市变得无法居住。
C1 adjective /ˌʌnrɪˈfaɪnd/

unrefined

未精炼的
Meaning
not processed or purified; lacking polish or sophistication
Example
The unrefined oil must be processed before it can be used as fuel.
未精炼的石油在用作燃料之前必须进行加工。
C2 noun /ˈʌndərlɪŋ/

underling

下属
Meaning
a person of low rank or importance; a subordinate
Example
The manager ordered his underlings to finish the task quickly.
经理命令他的下属快速完成任务。
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。
C1 noun /ˈʌndərˌwɜːrld/

underworld

地下世界
Meaning
The criminal world of organized crime or the mythical world of the dead.
Example
The detective spent years studying the secrets of the underworld.
侦探花了很多年研究地下世界的秘密。
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。
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。
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?
A2 adjective /ʌnˈlʌki/

Unlucky

倒霉; 不幸运
Meaning
having bad luck; unfortunate
Example
He was unlucky to miss the winning shot.
他很倒霉错过了获胜的投篮。
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。
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。
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。
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。
B2 adjective /ʌnprəˈfɛʃ.ən.əl/

Unprofessional

不专业
Meaning
not conforming to the standards expected in a particular profession
Example
His unprofessional behavior led to his dismissal from the company.
他的不专业行为导致他被公司解雇。
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 verb /ɜːrdʒ/

urge

催促
Meaning
to strongly encourage or try to persuade someone to do something
Example
Doctors urge patients to exercise regularly.
医生鼓励病人定期锻炼。
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。
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 /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 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。
A2 noun /ʌmˈbrɛlə/

umbrella

伞
Meaning
A device used for protection against rain or sun, typically consisting of a collapsible canopy mounted on a central rod.
Example
She opened her umbrella as it started to rain.
下雨时她打开了她的伞。
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 /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 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。
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。
B1 preposition, adverb, adjective /ˌʌndərˈniːθ/

underneath

在……下面
Meaning
Located directly below or beneath something
Example
The keys were hidden underneath the pile of papers.
钥匙被隐藏在那堆文件下面。
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。
B1 adjective /ʌnˈfeər/

Unfair

不公平; 不正当;
Meaning
not right or just; treating people in a way that favors some over others
Example
It's unfair to blame her for something she didn't do.
指责她做了她没有做的事是不公平的。
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。
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。
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。
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。
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。
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。
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 noun ˌɜːbənaɪˈzeɪʃən

urbanization

城市化
Meaning
The process by which towns and cities are formed and become larger as more people begin living and working in central areas.
Example
Urbanization leads to more developed infrastructure.
城市化导致更先进的基础设施。
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。
B1 noun /juːˈten.səlz/

Utensils

餐具
Meaning
tools or implements used for cooking, eating, or serving food
Example
Please wash all the cooking utensils after preparing dinner.
请在准备晚餐后清洗所有的厨房用具。
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。
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。
B2 noun /ʌnˈsɜːrtənti/

Uncertainty

不确定性; 怀疑或缺乏确信
Meaning
the state of being uncertain; doubt or lack of sureness
Example
The uncertainty about the weather delayed our trip.
关于天气的不确定性延迟了我们的旅行。
C1 adjective /ˌʌn.əˈdʌl.tə.reɪ.tɪd/

Unadulterated

纯净的
Meaning
not mixed or diluted with any different or extra elements; pure
Example
She felt unadulterated joy when she heard the news.
当她听到这个消息时，她感到纯净的快乐。
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。
A2 verb /ʌpˈset/

upset

烦扰
Meaning
to make someone worried, sad, or angry; to disturb
Example
The bad news upset everyone.
坏消息 upset 每个人。
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。
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。
C1 adjective /ʌnˈsoʊld/

unsold

未售出的
Meaning
not sold; remaining without a buyer
Example
The unsold goods were returned to the warehouse.
未售出的商品被退回仓库。
C1 noun /ˈʌp.rɔːr/

Uproar

骚动; 喧嚣; 混乱
Meaning
a loud and emotional noise or disturbance; public outcry
Example
The announcement caused an uproar among the students.
公告在学生中引起了骚动。
C1 noun ˈʌp.raɪ.zɪŋ

uprising

起义
Meaning
An act of resistance or rebellion; a revolt against an authority or government.
Example
The uprising marked the beginning of the revolution.
起义标志着革命的开始。
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。
C1 adjective /ʌnˈɜːrθli/

unearthly

超自然的
Meaning
Strange or unnatural in a way that seems not of this world
Example
The forest was filled with an unearthly glow.
森林中充满了超自然的光辉。
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。
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 verb /ˌʌndərˈɛstɪmeɪt/

underestimate

低估
Meaning
To judge something as less important or smaller than it really is.
Example
Never underestimate the power of teamwork.
永远不要低估团队合作的力量。
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。
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。
C1 noun /ˈʌndərˌteɪkər/

undertaker

殡葬员
Meaning
A person whose job is to prepare the dead for burial and arrange funerals.
Example
The undertaker prepared the body for the funeral service.
殡葬员为葬礼服务准备了尸体。
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 /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。
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。
C1 adjective /ˌjuːnɪˈsɛljʊlər/

unicellular

单细胞
Meaning
Consisting of a single cell.
Example
Amoebas are unicellular organisms.
变形虫是单细胞生物。
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。
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 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。
B2 adjective /ʌnˈbreɪkəbəl/

Unbreakable

不能被打破或损坏；非常强大和耐用
Meaning
not able to be broken or damaged; very strong and durable
Example
Their friendship formed an unbreakable bond.
他们的友谊形成了一个坚不可摧的纽带。
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。
A1 preposition/conjunction /ʌnˈtɪl/

until

直到
Meaning
up to the time of
Example
I will wait until you come back.
我会等到你回来。
C1 adverb /ʌnˈnætʃrəli/

unnaturally

不自然地
Meaning
in a way that is not natural or normal; excessively or strangely
Example
He smiled unnaturally, making everyone feel uncomfortable.
他不自然地笑了，让每个人都感到不舒服。
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 /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 /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 adjective /ˌʌnfɔːrˈsiːn/

unforeseen

Meaning
Not anticipated or predicted; unexpected.
Example
The project faced unforeseen challenges that delayed its completion.
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。
C1 adjective /ˌʌndərˈsteɪtɪd/

understated

低调的
Meaning
Presented in a subtle and restrained way.
Example
She wore an elegant but understated dress.
她穿了一件优雅但低调的裙子。
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.
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。
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 /ˈʌp.raɪt.nəs/

Uprightness

正直; 正义
Meaning
the quality of being honest and morally correct; integrity
Example
His uprightness in business dealings earned him great respect.
他在商业中的正直赢得了很大的尊重。
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。
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 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。
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。
B1 verb /ʌnˈræp/

unwrap

拆开
Meaning
remove wrapping or covering from something; reveal something gradually or clearly
Example
She carefully unwrapped the gift with excitement.
她兴奋地小心拆开了礼物。
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。
A1 pronoun /ʌs/

us

我们
Meaning
used to refer to the speaker and one or more other people as the object of a verb or preposition
Example
She gave us a gift.
她给了我们一个礼物。
C1 noun /ˌʌl.tɪˈmeɪ.təm/

Ultimatum

最后通牒
Meaning
a final demand or statement of terms, the rejection of which will result in retaliation
Example
The boss gave him an ultimatum: improve or be fired.
老板给了他一个最后通牒：要么改进，要么被解雇。