run-in \ˈ ̷ ̷ˌ ̷ ̷\noun (-s) Etymology:run in 1.: something inserted as a substantial addition in copy or typeset matter 2.Britain: the finish of a race or hunt 3.: tiff, altercation, quarrel < run-ins of tourists with taximen — A.D.Sheffield > 4.: the operation of running in a new engine or machine