retardation

plural retardations

1. The act of retarding or delaying; hindrance.
   1. countableuncountableacousticsThe distance by which one wave is behind another.

      Synonyms: delay, detention, hinderance, impediment

   2. countableuncountableentertainmentThe act of diminishing the rate of speed.

      Synonyms: delay, detention, hinderance, impediment

   3. countableuncountablecommunicationsA decrease in the speed of telegraph signalling.

      Synonyms: delay, detention, hinderance, impediment

2. countableuncountableThe extent to which anything is retarded; the result of any retarding or delay; mental, social, or physical slowness.
3. abbreviationcountableellipsisuncountablehuman sciencesEllipsis of mental retardation.

   Me and my friends used to feed LSD to this little retarded girl in our neighborhood and we'd lock arms around her and go "nightmare! Nightmare! Nightmare! Nightmare! Nightmare! Nightmare! Nightmare! Nightmare!" It actually cured her retardation.

   2014, The Eric Andre Show, season 3, episode 6, Eric Andre (actor)

4. colloquialcountablederogatoryoffensiveuncountableExtreme stupidity.
5. countableuncountableThat which retards; an obstacle; an obstruction.
6. countableuncountablenatural sciencesDeceleration; 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

   1 more example

   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 retardation in its velocity in December. Such a piece of news was scarcely calculated to interest a world the greater portion of whose inhabitants were unaware of the existence of the planet Neptune, nor outside the astronomical profession did the subsequent discovery of a faint remote speck of light in the region of the perturbed planet cause any very great excitement. Scientific people, however, found the intelligence remarkable enough, even before it became known that the new body was rapidly growing larger and brighter, that its motion was quite different from the orderly progress of the planets, and that the deflection of Neptune and its satellite was becoming now of an unprecedented kind.

   1897, H. G. Wells, The Star (Science Fiction)

7. countableuncountableentertainmentA suspension which resolves upwards.