Another time; once more.

Over and above a factor of one.

Used metalinguistically, with the repetition being in the discussion, or in the linguistic or pragmatic context of the discussion, rather than in the subject of discussion.

"Great, thanks again!"

Back in the reverse direction, or to an original starting point.

"Bring us word again."

Back (to a former place or state).

"The South will rise again."

In return, as a reciprocal action; back.

In any other place.

On the other hand.

Moreover; besides; further.

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 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."

In competition with, versus.

"The Tigers will play against the Bears this weekend."

Contrary to; in conflict with.

"Doing this is against my principles."

In opposition to.

"Are you against freedom of choice?"

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.

"The studio weren't sure the movie would ever get made, so they only paid $50,000 against $200,000. That way they wouldn't be out very much if filming never began."

Exposed to.