/ Dictionary / Index M monoamine oxidase inhibitor: Meaning and Definition of Find definitions for: mon'oamine' ox'idase inhib"itor Pronunciation: [key] any of various substances, as isocarboxazid and phenelzine, that block enzymatic breakdown of certain monoamine neurotransmitters: used to treat severe depression. Abbr.: MAOI Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. monoamine oxidase monoammonium phosphate Related Content Daily Word Quiz: secular Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language