6104.unconscious(形)无意识的
反义词conscious
I was unconscious of her presence．
我不知道她在场。

6105.unconsciously(副)无意识地
Perhaps,unconsciously, I've done something to offend her．
我也许无意中做了什么得罪她的事。

6106.underdeveloped(形)发育不全的
反义词developed
They voted aid for the underdeveloped countries in Asia.
他投票建议援助亚洲的不发达国家。

6107.underestimate(动)低估
反义词overestimate
Those who underestimate the intelligence of the rivals will come to grief.
低估对手智慧的人会大吃苦头的。

6108.undergo(动)经历；接受
不规则变化underwent，undergone
My mother underwent major surgery last year．
我母亲去年动过大手术。

6109.undergraduate(名)大学生；大学肄业生
She read histoy as an undergraduate.
她在大学攻读历史。

6110.undermine(动)在无形中损坏；削弱……的基础
Streams undermine the rocks.
流水侵蚀岩石的基部。

6111.underneath(介)在……下面
The coin rolled underneath the piano．
硬币滚到了钢琴底下。

6112.undertake(动)承担；保证
不规则变化undertook，undertaken
He undertook to pay the money back within six months．
他保证六个月内还钱。

6113.underworld(名)下层社会；黑社会
The police has informer in the London underworld.
警察在伦敦的下流社会中有告密者。

6114.undoubtedly(副)无疑地
There is undoubtedly a great deal of truth in what he says.
他所说的的确太部分都是实情。

6115.undress(动)脱下
She undressed and got into bed．
她解衣上床了。

6116.undue(形)过度的、过分的
同义词excessive
They are taking undue advantage of the situation.
他们过分利用了这种情势。

6117.uneasy(形)不当的、不舒服的
同义词anxious
I am uneasy in my mind about the future．
我为前途担忧。

6118.unemployed(形)失业的
How long have you been unemployed?
你失业多久了？

6119.unemployment(名)失业；失业人数
Unemployment hurts every person the country, not just those who have lost their jobs.
失业对国内的每一个人都有害，而不仅是那些丢饭碗的人。

6120.unexpected(形)意外的
同义词suffer
I'm afraid the unexpected accident may botch up the dinner today.
恐怕这意想不到的事故会把今天的晚宴搞糟。

6121.unexpectedly(副)意外地、未料到地
They had arrived unexpectedly.
他们意外地到达了。

6122.unforgettable(形)难忘的
The war has branded an unforgettable lesson on our minds．
战争在我们心上烙下了永生难忘的教训。

6123.unfortunate(形)不幸的
反义词fortunate
He was unfortunate to lose in the final round,
他不幸在最后一轮输了。

6124.unfortunately(副)不幸地
She had left for work unfortunately.
遗憾的是她已上班去了。

6125.unify(动)统一
In my opinion, Abraham Lincoln was honored mostly in the US because he unified the country.
在我看来，美国人敬重林肯，主要是因为他保持了美国的统一。

6126.union(名)工会；结合
In union there is strength.
团结就是力量。

6127.universal(形)全世界的；全盘的
The government introduced universal secondary education years ago.
几年前，政府就倡导普及中等教育。

6128.universe(名)宇宙
They thought the earth was the center of the universe.
他们认为地球是宇宙的中心。

6129.unknown(形)未知的(名)无名之士
(形):The idtentity of the bombers remained unknown．
这些轰炸机的来路依然不明。
(名):The author had been an unknown.
这个作家一直默默无闻。

6130.unlimited(形)无限的
反义词limited
Some of us have known for many, many years that the freedoms under the First Amendment are not totally unlimited.
我们有些人多年以来一直知道第一修正案授予的自由并不是完全没有限制的。

6131.unload(动)从……卸下
Everyone helped unload the luggage from the car.
大家都帮着从汽车上卸行李。

6132.unlock(动)打开锁、开启
How can we unlock all the secrets of nature?
我们怎样才能揭示大自然的全部奥秘呢？

6133.unnecessary(形)不必要的
反义词necessary
They were found guilty af causing unnecessary suffering to animals.
他们因虐待动物而被判有罪。

6134.unofficial(形)非正式的
同义词unlawful
Unofficial estimates put the figure at over2 million．
非官方的估计数字为200万以上。

6135.unpleasant(形)令人不愉快的
The minerals in the water made it unpleasant to drink.
水里的矿物质使得这水挺难喝的。