/therr"tee/ , n. , pl. thirties , adj.
n.
1. a cardinal number, 10 times 3.
2. a symbol for this number, as 30 or XXX.
3. a set of this many persons or things.
4. Print. , Journalism. 30-dash.
5. thirties , the numbers, years, degrees, or the like, from 30 through 39, as in referring to numbered streets, indicating the years of a lifetime or of a century, or referring to degrees of temperature: He works in the East Thirties. She must be in her thirties. The temperature was in the thirties yesterday.
adj.
6. amounting to 30 in number.
[ bef. 900; ME thritty, OE thritig, equiv. to thri THREE + -tig -TY 1 ; c. D dertig, G dreissig, ON thrjatiu ]