(about a new law, rule, etc.) intended to take effect from a particular date in the past rather than from the present date（新法律、规则等）追溯既往的，有追溯效力的◆retrospective pay awards有追溯效力的加薪◆retrospective legislation有追溯效力的立法▸ˌretroˈspectively ( ˌretroˈactively)
adverb
◆The new rule will be applied retroactively.新规则将具有追溯效力。