retard

(noun) a person of subnormal intelligence. Synonyms: idiot, imbecile, cretin, moron, changeling, half-wit.

(verb) cause to move more slowly or operate at a slower rate. Example: "This drug will retard your heart rate."

(verb) be delayed.

(verb) slow the growth or development of. Synonyms: check, delay. Example: "The brain damage will retard the child's language development."

(verb) lose velocity; move more slowly. Synonyms: decelerate, slow, slow down, slow up. Example: "The car decelerated."