Thirty \Thir"ty\, n.; pl. {Thirties}. 1. The sum of three tens, or twenty and ten; thirty units or objects. 2. A symbol expressing thirty, as 30, or XXX.
thirties n 1: the time of life between 30 and 40 [syn: {mid-thirties}, {thirty-something}] 2: the decade from 1930 to 1939 [syn: {1930s}]