ruò​zhì

idiotic

弱智 ruò​zhì
idiotic adjective
behaving in an extremely stupid, senseless, or moronic manner

He always asks very idiotic questions.

mentally deficient adjective
having a congenital or developmental intellectual disability

That institution is dedicated to providing special education for children with intellectual disabilities.

Frequency

Movie subtitles
7.12 per million appears in 3% of films
Written text
3.86 per million

Sources

Definitions
CC-CEDICT