Definition of "HM"

HM

noun
plural HMs
1. Initialism of His Majesty (the title of a king).
2. Initialism of Her Majesty (the title of a queen).
3. (India, government) Initialism of Home Minister.
4. (military, US) Abbreviation of hospital corpsman.
5. (music) Abbreviation of heavy metal.
  Quotations
  When girls appropriate a male-dominated form like HM, can they discard its sexist content without replacing it with something else?
  1982 April 24, “Women of Iron”, in Gay Community News, page 10
proper noun
1. (computing theory) Initialism of Hindley-Milner.