Flex or fold

The act of “putting your money where your mouth is” by rising to the occasion or backing down. Much like “nut up or shut up”, it is a challenge to someone who has said that they would do something to show strength—usually an aggressive or bold course of action. It is frequently an ultimatum to call someone’s bluff after they’ve been running off at the mouth about what they could or would do in any given situation. The term is used to shut down foolish declarations made by wanna-be types who have something to prove to themselves and others, but they often lack the ability to follow through.