The decade of the 1880s, 1980s, etc.
The decade of one's life from age 80 through age 89.
(temperature, rates) The range between 80 and 89.
From or evoking the 81st through 90th years of a century (chiefly the 1980s).
Sue picked a playlist of eighties music for the dinner to remind her wife of that night they met all those years ago.