retarded
re-tar-ded
adjective
(Offensive, outdated) Having an intellectual disability or learning difficulty.
"Using 'retarded' to describe people is offensive."
adjective
Having been slowed down or delayed in development or progress.
"The plant's growth was retarded by frost."
Thesaurus
Synonyms: slow-witted, delayed, backward, cretinous, dim-witted, simple-minded, imbecile, imbecilic, moronic, simple, idiotic, half-witted
Antonyms: precocious