retarded

adjective5

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

   • This kind of plant is usually of a retarded growth.
2. •
   (offensive, old-fashioned) Having mental retardation; mentally deficient or underdeveloped.

   • Experts in the field say there are now at least 200,000 retarded people over 60 in the United States. — 1990
3. •
   (offensive, old-fashioned) Specifically, having an IQ below 70.
4. •
   (informal, offensive) Extremely stupid; obtuse

   • Looking at Jack, Gabbie said, "What?" "That's the Troll Bridge." She groaned at the pun. "That's retarded." — 1988
5. •
   Designating a parameter of an electromagnetic field which is adjusted to account for the finite speed of radiation.