feebleminded

feebleminded /ˌfiːbəlˈmaɪndəd/ adjective
feebleminded
/ˌfiːbəlˈmaɪndəd/
adjective
Britannica Dictionary definition of FEEBLEMINDED
[more feebleminded; most feebleminded]
1 
old-fashioned + offensive : having less than normal intelligence
2 
: foolish or stupid : not sensible

— feeblemindedness

noun [noncount]