knock off . knock off {v. phr.}, {slang} 1. To burglarize someone. They knocked off the Manning residence. 2. To murder someone. The gangsters knocked off Herman. Categories: add yours {slang} {v. phr.} Source: A Dictionary of American Idioms by A. Makkai, M.T. Boatner, J.E. Gates © 2024 To section: K Subscribe to: American IdiomsIdioms feedEnglish languageHome page and general feed Comment on this entry