1、 表示“反对”“对着”“违反”“不利于”等。如：
We are all against his idea、我们都反对他的想法。
He was married against his will、他结婚是有违本意的。
He spoke against the new law、他发言抨击新法律。
There were 20 votes for him and 12 against him、有20票赞成他，12票反对他。
2、 表示“靠着”“顶着”“迎着”“衬着”等。如：
He stood with his backagainstthe door、他背靠门站着。
He hit his head against the window、他的头撞到了窗户上。
It is difficult to see anything against this bright light、对着这种强光很难看到任何东西。
Bright red flags flow in the wind against the blue sky、鲜艳的红旗映着蓝天迎风飘扬。
3、注意against是介词，不是动词。如：
他靠在树上。
正：He leanedagainstthe tree、
误：He against the tree、
这个计划你是赞成还是反对呢?
正：Are you for or against the plan?
误：Do you support or against the plan?
4、正因为against是介词，所以后接动词时要用动名词。如：
我反对在警察到达之前采取任何行动。
正：I’m against doing anything till the police arrive、
误：I’m against to do anything till the police arrive、