let sb off (with sth)
not punish sb (severely) 不(严厉)惩罚某人
She was let off with a fine instead of being sent to prison. 没让她入狱, 而是罚款了事.
Don´t let these criminals off lightly, ie Punish them severely. 不要轻易放过这些罪犯. let sb off (sth) not compel sb to do (sth) 不强迫某人做(某事物)
We´ve been let off school today because our teacher is ill. 今天学校放假, 因为我们的老师病了. let sth off fire sth off; explode sth 放枪炮、 烟火等
The boys were letting off fireworks. 男孩子在放烟火.