retardation

Etymology

retard + -ation

noun

1. The act of retarding or delaying; hindrance.
   1. (acoustics) The distance by which one wave is behind another.
   2. (music) The act of diminishing the rate of speed.
   3. (telegraphy) A decrease in the speed of telegraph signalling.
2. The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
3. (colloquial, derogatory, offensive) Extreme stupidity.
4. That which retards; an obstacle; an obstruction.
5. (physics) Deceleration; reduction in the magnitude of velocity.
   … the effect is automatically to select a braking force which is higher at above 40 m.p.h., in the initial stages of retardation, but is reduced as the speed falls below 40 m.p.h. 1960 April, “The braking of trains”, in Trains Illustrated, page 237
6. (music) A suspension which resolves upwards.