/ Dictionary / Index O O.H.M.S.: Meaning and Definition of Find definitions for: O.H.M.S. Pronunciation: [key] On His Majesty's Service; On Her Majesty's Service. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: ohms (Thesaurus) ohmmeter Ohm's law Related Content Daily Word Quiz: cautious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language