/ Dictionary / Index F first mate: Meaning and Definition of Find definitions for: first' mate' Pronunciation: [key] the officer of a merchant vessel next in command beneath the captain. Also called Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. firstly first messenger Related Content Daily Word Quiz: illegible Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language