I. ˈbīˌgȯn adjective
Etymology: Middle English (Scots dialect) bygane, from by (II) + gane, variant of gon, past participle of gon to go — more at go
1. : that is past : gone by : former
the music of a bygone day
2.
a. : of or relating to the past : outmoded
current fashions … are revivals of bygone styles — P.M.Gregory
b. : no longer living : dead , extinct
circles of burned and broken stone remain as evidence of its popularity with bygone tribes — American Guide Series: Michigan
bygone species of animals — Weston LaBarre
II. noun
( -s )
1. : something that is past ; especially : a past grievance — usually used in plural
a gesture to show that bygones are bygones — William Walton
let bygones be bygones
2. : one that belongs to the past
to them he is a bygone — Bookman
a museum in search of bygones — H.V.Morton