| 3. | nineties - the time of life between 90 and 100time of life - a period of time during which a person is normally in a particular life state eld, geezerhood, old age, years, age - a late time of life; "old age is not for sissies"; "he's showing his years"; "age hasn't slowed him down at all"; "a beard white with eld"; "on the brink of geezerhood" | |