A slowing or hindrance.

(often in combination) Serving to impede (slow down) the action of something

(often in combination) Something that serves to retard (slow down) the action of something

Something which retards or slows. / (mechanical engineering) A device for slowing down large trucks, lorries, buses, shunted railway wagons.

plural of retardant

plural of retarder

(technical) A retarded person; a person with retardation.

plural of retardate

That retards; delaying, impeditive.

Retardation; delay. / (music) A slowing down of the tempo; a ritardando. / (offensive, dated) A person with mental retardation.