History, etymology, and pronunciation of m, the thirteenth letter in the alphabet. It corresponds to the Semitic mem and to the Greek mu. The Semitic form may derive from an earlier sign representing waves of water. The sound represented by the letter has been from the beginning the labial nasal., From upper case roman numeral M (1000), an alteration of ⋈, from ∞, an alteration of ↀ, an alteration of Ⓧ, from encircling X (the roman numeral for ten) to indicate the hundredth ten., M or m is a written abbreviation for words beginning with m, such as 'minutes', 'married', 'male', and 'masculine'., Define M. M synonyms, M pronunciation, M translation, English dictionary definition of M. also m The symbol for the Roman numeral 1,000. abbr. 1. Printing em 2. Bible Maccabees 3. Mach number 4. male 5. married 6. medium 7. meridian 8., Visit any of our M&M’S store locations for a colorful, fun experience. Enjoy all of our M&M’S character moments, shop our chocolate gifts & personalized chocolate., any spoken sound represented by the letter M or m, as in my, summer, or him. something having the shape of an M. a written or printed representation of the letter M or m..