1. slang An instruction, usually said in frustration, for someone to stop intruding in one's business or conversation. Butt out, sis—I don't need your opinion on everything I do!
2. slang To leave a place hastily. We butted out of the party when we heard sirens approaching.
exclam. Get out of my affairs!; Mind your own business! Go away! Butt out!
See also: butt