retro

Short definition from Wiktionary

Adjective

1. 1
   Of, or relating to, the past, past times, or the way things were.
2. 2
   Affecting things past; retroactive, ex post facto.

Noun

1. 1
   Past fashions or trends.
2. 2
   Abbreviation of retrorocket.
3. 3
   Abbreviation of retrospective.
4. 4
   A chess puzzle of retrograde analysis, requiring the solver to work out the history of moves leading to the position presented.