The decade of the 1860s, 1960s, etc. (but especially the 1960s)
A period in American history centered around the counterculture movement of the late 1960s.
The decade of one's life from age 60 through age 69.
(temperature, rates) The range between 60 and 69.
Highs in the mid sixties.
From or evoking the 61st through 70th years of a century (chiefly the 1960s).