A mustache grown out by a man for a specific cause or awareness, usually a charity. It can also refer to a situation in which a man pledges to shave off the mustache he wears regularly if a certain variable is met.
1. Guy: What is that?
Guy 2: It's a charity stache. We're growing out mustaches in support of cancer research.
Guy: Oh, that's cool.
2. Coach Burnett says he will shave off his mustache if the 1st period boys basketball team wins the home room canned food drive.