retardation

Noun

retardation (countable and uncountable, plural retardations)

1. (acoustics) The distance by which one wave is behind another.

   Synonyms:

   delay, detention, hinderance, impediment

2. The act of diminishing the rate of speed.

   Synonyms:

   delay, detention, hinderance, impediment

3. A decrease in the speed of telegraph signalling.

   Synonyms:

   delay, detention, hinderance, impediment

4. The extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
5. (colloquial, derogatory, offensive) Extreme stupidity.
6. That which retards; an obstacle; an obstruction.
7. Deceleration; reduction in the magnitude of velocity.
   • It was on the first day of the new year that the announcement was made, almost simultaneously from three observatories, that the motion of the planet Neptune, the outermost of all the planets that wheel about the sun, had become very erratic. Ogilvy had already called attention to a suspected...1897, H. G. Wells, The Star (Science Fiction)
   • [...] 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
8. A suspension which resolves upwards.