/ Dictionary / Index S second messenger: Meaning and Definition of Find definitions for: sec'ond mes'senger Pronunciation: [key] — Biochem. Biochem. any of various intracellular chemical substances, as cyclic AMP, that transmit and amplify the messages delivered by a first messenger to specific receptors on the cell surface. Cf. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. secondment second mortgage Related Content Daily Word Quiz: sinister Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language