retard

verb (used with object)

1. to make slow; delay the development or progress of (an action, process, etc.); hinder or impede.

verb (used without object)

2. to be delayed.

noun

3. a slowing down, diminution, or hindrance, as in a machine.
4. Slang: Disparaging and Offensive.
   1. a contemptuous term used to refer to a person who is cognitively impaired.
   2. a person who is stupid, obtuse, or ineffective in some way: a hopeless social retard.
5. Automotive, Machinery. an adjustment made in the setting of the distributor of an internal-combustion engine so that the spark for ignition in each cylinder is generated later in the cycle.

verb (rɪˈtɑːd)

1. (tr) to delay or slow down (the progress, speed, or development) of (something)

noun (ˈriːtɑːd)

2. US offensive a retarded person
3. US offensive a foolish person

v.

late 15c., “make slow or slower,” from French retarder “restrain, hold (someone) back, keep (someone from doing something); come to a stop” (13c.) or directly from Latin retardare “make slow, delay, keep back, hinder” (see retardation). Related: Retarded; retarding.

The noun is recorded from 1788 in the sense “retardation, delay;” from 1970 in offensive meaning “retarded person,” originally American English, with accent on first syllable. Other words used for “one who is mentally retarded” include retardate (1956), retardee (1971).