What does the idiom against mean?

The idiom "against" is not a single idiom on its own. It's a preposition that is used in many idiomatic expressions. To understand its meaning, we need to look at the specific idiom it's used in.

Here are some examples of how "against" is used in idioms, and their meanings:

* Against all odds: Despite facing many challenges or difficulties.

* Against the grain: Contrary to one's natural inclination or what is expected.

* Go against the flow: To act differently from the majority or the accepted way.

* Up against it: Facing a difficult situation or challenge.

* Run against the clock: To work quickly and efficiently to finish something before a deadline.

* Against the law: Illegal, forbidden.

* Lean against: To rely on someone or something for support.

In general, "against" in idioms often implies opposition, conflict, or a clash of some sort. It can also indicate resistance, defiance, or a challenge to the expected or normal.

To understand the specific meaning of an idiom with "against," you need to consider the context and the other words used in the phrase.