Mg Definition

abbreviation
Milligram(s)
Webster's New World
Machine gun.
Webster's New World
Major General.
Webster's New World
Middle guard.
Webster's New World
Military government.
American Heritage
symbol
Magnesium.
Webster's New World

(metrology) Symbol for the milligram, an SI unit of mass equal to 10−3 grams.

Wiktionary

(metrology) Symbol for the megagram, an SI unit of mass equal to 106 grams.

Wiktionary