Noun
Thompson submachine gun (plural Thompson submachine guns)
A .45-caliber American submachine gun, having a wooden stock and a drum, stick, or box magazine.
Krause Publications. 2000. pages 116 The Thompson submachine gun had been in development at approximately the same time as the Bergmann and the Beretta. Source: Internet
These were true hand-held machine pistols, which were fitted with Thompson submachine gun Model 1921 vertical grips on their dust covers, an extended barrel with muzzle brakes similar to the Thompson's, an extended 20-round magazine. Source: Internet