M

Universal Words noun, abbreviation, symbol noun (also m) [C,U] (plural M's, m's ) the 13th letter of the English alphabet: 'Milk' begins with (an) M / 'M'. abbreviation 1 (also med.) (especially for sizes of clothes) medium: S M and L (= small, medium and large) 2 (used with a number to show the name of a British motorway): heavy traffic on the M25 symbol (also m) the number 1000 in ROMANNUMERALS