let off . explode；fire；release放（枪、炮、烟火等）；排放
The boys were letting off fireworks．孩子们在放烟火。
The engine let off steam in sudden blasts．机车突然放出一股蒸汽来。
In honour of the distinguished guest．they let off a salute of twenty-one guns．为向贵宾表示敬意，他们鸣礼炮二十一响
let off . excuse from a penalty 免罚
Two boys were caught smoking in the school but the principal let them off with a warning．两个男孩在学校抽烟，不过校长对他们提出警告后放了他们。
With your record， you can hardly expect to be let off lightly．你有前科， 很难指望会从轻发落。
She forgot her lines again ; but she was let off once more她再次忘记台词又没有受到批评。
The magistrate told the youths he would let them off this time but that they would be severely punished if they appeared before him again．地方法官告诉这些年轻人；他这次放过他们，但如果他们再次在他面前出现，他们将受到严惩。
let off . discharge；allow to get off 卸下；让…离开
The train stops to let off passengers on signal．这列火车按信号停车让旅客下车。
I asked the captain to let me off at the next port of call．我请求船长在下个停靠岸让我下船。
let off . excuse from a task or an obligation免除任务或责任等
Mary's mother said that she would let Mary off from washing the supper dishes．玛丽的母亲准许玛丽晚餐的碗碟不洗了。
The factory closed for a month in the summer and let the workers off．工厂夏天停工一个月，放了工人的假。
let off . lease in portions；allow to rent a building in portions 分开出租
The five floors of this large building were let off as separate flats．这座大楼的五层全都分为套间出租。
let on . allow to be known；reveal one's knowledge of 泄露（常用于否定式）
Don't let on that I told you．不要说出我告诉了你。
She was terrified at the information，but didn't let on．她听到消息十分害怕，但没有泄露。
Don't let on about what they did．不要讲他们干的事。
let on . pretend；make believe 假装；装做
He let on that he did not see me．他装做没有看见我。
She is not as rich as she lets on．她并不象她装得那样有钱。
They let on that they didn't care about not being invited，but I could tell they were hurt．他们未被邀请，作出满不在意的样子，但是我知道他们的自尊心受到了伤害。
He got the job by letting on that he had a lot of experience．他装着很有经验的样子得到了这份工作。
let onto . reveal；inform；tell 告诉；通知
Don't let onto Helen that we are planning to go to the movies tonight．不要告诉海伦我们今晚要看电影。
let out . rent out 租出去
He used to let out cars．他过去出租汽车。
In the park boats are let out for three yuan per hour．在公园里，可以以每小时三元的价格出租小游艇。
let out . allow to go out or escape 放出
The guard let the prisoners out of jail to work in the garden．看守放犯人出牢房，在园子里干活。
Let me out！I'm locked in！让我出来！我被锁在里面了！
The doctor is letting her out of hospital next week．医生打算下周让她出院。
let out . tell；reveal 泄漏
I'll never tell you another secret if you let this one out．假如你把这个机密泄漏出去，有秘密的事我再也不告诉你了。
Who let out the exam results? They were supposed to be confidential until tomorrow．谁泄露了考试结果? 他们应该保密到明天。。
Someone has let the news out．有人把这个消息泄露出去了。
let out . make larger 放大
Mary's mother had to let out Mary's dress because she was growing so tall．玛丽的母亲不得不把玛丽的衣服放大些，因为玛丽长得那么高。
If she gets much fatter she will have to let out all her dresses．如果她继续发胖，她所有的衣服都得放宽。
let out . dismiss 解雇；革职；开除
The shop closed down and all the men were let out．店关了门，所有的员工都被辞退了。
let out . terminate；be finished；end（学校）放学；（戏院）散场；（训练）结束
When does the university let out for the summer? 大学何时放暑假?
The coach let us out from practice at three o'clock．训练到 三点钟，教练把我们解散了。
They were waiting for school to let out．他们在等学校放学。
let out . make（a sound）come out of the mouth；utter 自口中发出（声音）
A bee stung Charles．He let out a yell and ran home．一只蜜蜂咬了查理，他大叫一声跑回家了。
He let out a cry of pain as the nail went into his foot．钉子扎进他的脚时，他痛苦地大喊了一声。
let out . release from further responsibility；release from an obligation 免除进一步的责任；免除义务
I was glad to be let out of that nasty affair，and have someone more experienced handle the trouble．我高兴的是我从那件讨厌的事情中解脱了，已让另外一个更有经验的人去处理。
My flu let me out of attending the meeting．由于患了流感；我参加不了那个会了。
The regular teacher is back，that let me out．正式的老师回来了，我可以解脱了。
let out . release from restraint；allow to gather speed 使放开速度；让…加速前进
He turned into an express way and let the car out．他把车子转入高速公路，然后加速前进。
The rider let out his horse to try to beat the one ahead of him．骑士放马快跑想追上领先的那匹马。