n. pl. six·ties
1. The cardinal number equal to 6 × 10.
a. A decade or the numbers from 60 to 69: They planned to retire in their sixties. The breeze kept the temperature in the sixties.
b. often Sixties The decade from 60 to 69 in a century.
[Middle English, from Old English sixtig; see s(w)eks in the Appendix of Indo-European roots.]
sixty adj. & pron.
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