To diminish the velocity of motion; to hinder; to render more slow in progress; as, to retard the march of an army; to retard the motion of a ship. The resistance of air retards the velocity of a cannon ball. It is opposed to accelerate.

To delay; to put off; to render more late; as, to retard the attacks of old age; to retard a rupture between nations. My visit was retarded by business.

To stay back.