/ Dictionary / Index M M-1: Meaning and Definition of Find definitions for: M-1 Pronunciation: (em'wun'), [key] — pl. M-1's. a semiautomatic, gas-operated, .30 caliber, clip-fed rifle, with a weight of 8.56 lb. (3.88 kg): the standard U.S. Army rifle in World War II and in the Korean War. See illus. under Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease. See also: m-1 (Thesaurus) M-1 M-14 Related Content Daily Word Quiz: profiterole Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language