GM Definition

abbreviation
General Manager.
Webster's New World
Gram(s)
Webster's New World
Genetically modified.
Webster's New World
General merchandise.
Webster's New World
Grand Master.
Webster's New World
symbol

(metrology) Symbol for the gigameter (gigametre), an SI unit of length equal to 109 meters (metres).

Wiktionary

Other Word Forms of GM

Noun

Singular:
GM
Plural:
gms