/ Dictionary / Index M M-14: Meaning and Definition of Find definitions for: M-14 Pronunciation: (em'fôr"tēn', -fōr"-), [key] — pl. M-14's. a fully automatic, gas-operated, .30 caliber rifle developed from the M-1: replaced the M-1 as the standard U.S. Army combat rifle. Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. M-1 M-16 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