retroactive (adj.) Look up retroactive at Dictionary.com
1610s, from French rétroactif (16c.) "casting or relating back," from Latin retroact-, past participle stem of retroagere "drive or turn back," from retro- "back" (see retro-) + agere "to drive, set in motion" (from PIE root *ag- (1) "to drive, draw out or forth, move"). Related: Retroactively.