WordNet (r) 3.0 (2006):

hm
    n 1: a metric unit of length equal to 100 meters [syn:
         hectometer, hectometre, hm]

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

HM
       HyperMemory (graphics)


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

hm

    The country code for the Heard and McDonald
   Islands.

   (1999-01-27)