Flat busted, broke, penniless, can't rub two nickels together, tapped out, all are examples of ways to say you have no money. That you're poor or without funds.
This is not an idiom. When you see AS ___ AS ___ you are looking at A Simile. This is comparing two flat things.
Busted Flat Records was created in 2002.
Obviously, to fall flat is exactly that. However, as an idiom it refers to either a joke or some piece of advice or 'wise words' that nobody properly understands. So you say these words and everybody looks at one another and says "So what?" It will have fallen flat.
"Busted" can have a couple of meanings. Either you have been caught by the authorities doing something you shouldn't have been doing, or you have no money and are "flat broke."
well, an auntie is a person's aunt (mother or father's sister) a flat is an apartment
RFP is not an idiom. It's an abbreviation.
It's not really an idiom. It means "what are you thinking about."
It is not an idiom, it means your nose is itching.
it means to be busted
idiom means expression like a page in a book
It's not an idiom. It means the tip of your nostril.
"Sieve" is not an idiom. See the related link.