Het up means excited or agitated; heated up.
An idiom that means surrender is to "wave the white flag." A closely related idiom is to "throw in the towel" which means to give up."
It means things are trustworthy.
The idiom "crack someone up" means to make someone laugh or amuse them greatly.
It means that you will like it. Something you are interested in.
It means shut up!
It means to gather up enough courage to do something.
It means stay with the rest of the group.
It means "shut up" or "be quiet"
It means he's really angry.
It's not an idiom. It means exactly what it looks like.
The idiom buck up means to cheer up. For example one might say "she began to buck up once I showed her some photographs of her children when they were younger."
It means to concede defeat and stop trying.