precocious

Synonyms:

intelligent

having the capacity for thought and reason especially to a high degree

advanced

farther along in physical or mental development

Antonyms:

retarded

relatively slow in mental or emotional or physical development

stupid, unintelligent

lacking intelligence

backward, feebleminded, half-witted, slow-witted

retarded in intellectual development

idiotic, imbecile, imbecilic

having a mental age of three to seven years

moronic

having a mental age of between eight and twelve years

cretinous

afflicted with cretinism

delayed

not as far along as normal in development

dim-witted, simple, simple-minded

lacking mental capacity and subtlety

show more antonyms...

Synonyms:

early

being or occurring at an early stage of development