retardation

noun10

1. •
   The act of retarding or delaying; hindrance.
2. •
   The distance by which one wave is behind another.
3. •
   The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
4. •
   Ellipsis of mental retardation.
5. •
   The act of diminishing the rate of speed.
6. •
   A decrease in the speed of telegraph signalling.
7. •
   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
8. •
   (informal, offensive) Extreme stupidity.
9. •
   That which retards; an obstacle; an obstruction.
10. •
    A suspension which resolves upwards.