The polite form of Mush It In - referring to any act of intercourse following excessive ingestion of alcohol or drugs.
by Demarke May 23, 2013
A M.I.I. is a shortened was of saying mentily ill ingot. Which is a term used to describe a single mentally ill person in a polite-ish sort of way.
Based on the way the person is acting the old man said ro his friends "that person is a M.I.I." as to not upset the person by calling them mentally ill.
by The real Enlightener April 08, 2023