In a contrary direction to.
- It is hard work to swim against the current.
In physical opposition to; in collision with.
- The rain pounds against the window.
In physical contact with, so as to abut or be supported by.
- The ladder was leaning against the wall.
- The puppy rested its head against a paw.
- The kennel was put against the back wall.
Close to, alongside.
- A row of trees stood against a fence.
In front of; before (a background).
- The giant was silhouetted against the door.
In contrast or comparison with.
- He stands out against his classmates.
- This report sets out the risks against the benefits.
In competition with, versus.
- The Tigers will play against the Bears this weekend.
Contrary to; in conflict with.
- Doing this is against my principles.
- It is against the law to smoke on these premises.
- There was no car in sight so we crossed against the red light.
In opposition to.
- Are you against freedom of choice?
- He waged a ten-year campaign against the company that was polluting the river.
- I'd bet against his succeeding.
- (with implied object) Ten voted for, and three voted against.
Of betting odds, denoting a worse-than-even chance.
- That horse is fifty-to-one against, so it has virtually no chance of winning.
In exchange for.
- The vouchers are redeemable against West End shows and theatre breaks.
As counterbalance to.
As a charge on.
- Tax is levied against income from sales.
As protection from.
- He turned the umbrella against the wind.
In anticipation of; in preparation for (a particular time, event etc.).
- The stores are kept well stocked against a time of need.
(Hollywood) To be paid now in contrast to the following amount to be paid later under specified circumstances, usually that a movie is made or has started filming.