noun
A fully automatic firearm that fires rifle-caliber rounds; used in military and action contexts.
敵の機関銃が激しく火を噴いた。
The enemy machine gun fired fiercely.
その戦車には機関銃が搭載されている
The tank is equipped with a machine gun.
拳銃 is a handgun or pistol, much smaller and less powerful than a 機関銃.
Compound of 機関 (mechanism, engine) and 銃 (gun), literally 'mechanism gun'. The term was coined in the late 19th century as a calque of 'machine gun'.