Re`tar*da"tion (?), n. [L. retardatio: cf. F. retardation.] 1. The act of retarding; hindrance; the act of delaying; as, the retardation of the motion of a ship; -- opposed to acceleration.

The retardations of our fluent motion.
De Quinsey.

2. That which retards; an obstacle; an obstruction.

Hills, sloughs, and other terrestrial retardations.
Sir W. Scott.

3. (Mus.) The keeping back of an approaching consonant chord by prolonging one or more tones of a previous chord into the intermediate chord which follows; -- differing from suspension by resolving upwards instead of downwards.

4. The extent to which anything is retarded; the amount of retarding or delay.

Retardation of the tide. (a) The lunitidal interval, or the hour angle of the moon at the time of high tide any port; the interval between the transit of the moon and the time of high tide next following. (b) The age of the tide; the retard of the tide. See under Retard, n.