verb

1. To keep delaying; to continue to hinder; to prevent from progress

   “retard the march of an army”

2. To put off; to postpone.

   “to retard a rupture between nations”

3. To be slow or dilatory to perform (something).

Synonyms: decelerate, slow, slow down, slow up, decelerate, hinder, slow, slow down

adjective

1. Delayed; delayed in development, hindered; impeded.

2. Having mental retardation; mentally deficient or underdeveloped.

3. Specifically, having an IQ below 70.