retardation

retard +‎ -ation

retardation (countable and uncountable, plural retardations)

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.
   • 1960 April, “The braking of trains”, in Trains Illustrated, page 237:

     [...] 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.

6. (music) A suspension which resolves upwards.

• growth retardation
• mental retardation

• “retardation”, in The Century Dictionary […], New York, N.Y.: The Century Co., 1911, →OCLC.
• “retardation”, in Webster’s Revised Unabridged Dictionary, Springfield, Mass.: G. & C. Merriam, 1913, →OCLC.