WordNet (r) 3.0 (2006):

gm
    n 1: a metric unit of weight equal to one thousandth of a
         kilogram [syn: gram, gramme, gm, g]

V.E.R.A. -- Virtual Entity of Relevant Acronyms (February 2016):

GM
       General MIDI [standard] (MIDI)


The Free On-line Dictionary of Computing (30 December 2018):

gm

    The country code for Gambia.

   (1999-01-27)