move in on move in on {v. phr.}, {slang}, {colloquial} To take over something that belongs to another. He moved in on my girlfriend and now we're not talking to each other. Categories: add yours {colloquial} {slang} {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2025 To section: M Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Add my comment