From Longman Dictionary of Contemporary Englishtommy guntom‧my gun /ˈtɒmi ɡʌn $ ˈtɑː-/ noun [countable] old-fashioned informalPMW a gun that can fire many bullets very quickly
Examples from the Corpus
tommy gun• Between them was a tommy gun, discharging itself into the air.Origin tommy gun (1900-2000) Thompson submachine gun ((20-21 centuries)), from John T. Thompson (1860-1940), U.S. general who invented the gun 