Retardation

The act of retarding; hindrance; the act of delaying; as, the retardation of the motion of a ship; -- opposed to acceleration.

That which retards; an obstacle; an obstruction.

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.

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

lack of normal development of intellectual capacities