a. [ Cf. F. rétrogressif. ] 1. Tending to retrograde; going or moving backward; declining from a better to a worse state. [ 1913 Webster ]
2. (Biol.) Passing from a higher to a lower condition; declining from a more perfect state of organization; regressive. [ 1913 Webster ]
adv. In a retrogressive manner. [ 1913 Webster ]