tom ‧ my gun /ˈtɒmi ɡʌn $ ˈtɑː-/ BrE AmE noun [countable]
[ Date: 1900-2000 ; Origin: Thompson submachine gun (20-21 centuries) , from John T. Thompson (1860-1940), U.S. general who invented the gun ]
old-fashioned informal a gun that can fire many bullets very quickly