boss2Pronunciation: /bɒs/Translate boss | into French | into German | into Italian | into Spanish Definition of boss noun 1a stud on the centre of a shield. Architecture an ornamental carving covering the point where the ribs in a vault or ceiling cross. the central part of a propeller. 2 Geology a large mass of igneous rock protruding through other strata. Origin: Middle English: from Old French boce, of unknown originboss in other Oxford dictionaries Definition of boss in the US English dictionary