/ Dictionary / Index F first messenger: Meaning and Definition of Find definitions for: first' mes'senger Pronunciation: [key] — Biochem. Biochem. a hormone that triggers a biochemical reaction at a site removed from its release. Cf. second messenger. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. first mate first mortgage Related Content Daily Word Quiz: hedonist Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language