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
