From Halopedia, the Halo wiki
A submachine gun, abbreviated SMG, is a magazine-fed, automatic gun designed fire pistol cartridge.
Submachine gun may refer to the following:
Z-130 Suppressor - The Z-130 Directed Energy Automatic Weapon (Z-130 DEAW), also called the Suppressor, is a fully automatic Forerunner energy weapon. It is usually utilized by the Prometheans.