The Collaborative International Dictionary of English v.0.48:

eighties \eighties\ n.
   the decade from 1980 to 1989.
   [WordNet 1.5]

   2. the time of life between 80 and 90.

   Syn: mid-eighties.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

eighties
    n 1: the decade from 1880 to 1889 [syn: eighties, 1880s]
    2: the decade from 1980 to 1989 [syn: eighties, 1980s]
    3: the time of life between 80 and 90 [syn: eighties, mid-
       eighties]