When a male's subconscious went into the world of titties and football and ignored every VERY important thing the female said.
girl: "So Suzie said that she told Mary that Bob was... Are you listening to me?"
man: *no response*
girl: "Oh.My.God. You just totally manned out on me!"
when a young gay male becomes a grown man.
Jason just turned 29 but still felt 23. But he realized he had "manned out" when a younger East Village boy promptly told him, "You're cute, but aren't you like 30?"