/siks"tee/ , n. , pl. sixties , adj.
n.
1. a cardinal number, ten times six.
2. a symbol for this number, as 60 or LX.
3. a set of this many persons or things.
4. sixties , the numbers, years, degrees, or the like, from 60 through 69, as in referring to numbered streets, indicating the years of a lifetime or of a century, or noting degrees of temperature: Her grandfather is in his late sixties. The temperature is in the low sixties.
5. like sixty , Informal. with great speed, ease, energy, or zest: Everyone was working like sixty to finish up before the holidays.
adj.
6. amounting to 60 in number.
[ bef. 900; ME (adj. and n.), OE sixtig (adj.); c. D zestig, G sechzig, ON sextigir. See SIX, -TY 1 ]