SGM

noun3

1. •
   (US) Sergeant major.
2. •
   Sexual and gender minority/minorities, i.e. non-heterosexual and/or non-cisgender person(s). (Also used attributively.)

   • Such realities are indeed problematic for SGM youth, whose age and sexual and gender differences render them ... — 2015
3. •
   Initialism of spherical grating monochromator.