Prov. When one person loses something, another person gets it. (You can substitute appropriate names or pronouns for the phrases one man's and another man's, as in the second example.) Mike found a five-dollar bill on the sidewalk. "One man's loss is another man's gain," he thought to himself, as he took the money.Jane: Andy just got fired. Jill: I know. And Andy's loss is my gain; I'm getting promoted to his job!