feeble-minded 
adjective
1Unable to make intelligent decisions or judgements; foolish or stupid.They don't own any sign of scientific thinking and they just follow their feeble-minded instincts and make stupid decisions....
- After all, if you wander past many licensed premises in the early hours of the morning you are likely to hear subdued mutterings which the more feeble-minded are likely to interpret as ghosts.
- It was an easy way for society to lock up girls who were ‘frivolous, sinful and feeble-minded.’
Synonyms
stupid, idiotic, moronic, imbecilic, foolish, half-baked, half-witted, dim-witted, witless, dunce-like, doltish, cretinous, empty-headed, vacuous, vapid
informal daft, dumb, dim, dopey, dozy, birdbrained, pea-brained, fat-headed, lamebrained, chuckleheaded, dunderheaded, wooden-headed, muttonheaded, boneheaded, crazy, mental, nuts, nutty, crackers, cracked, potty, barmy, batty, cuckoo, bonkers, dotty, dippy
North American informal dumb-ass
1.1 dated (Of a person) having less than average intelligence.In 1930s Nazi Germany about 350,000 people, categorized most commonly as feeble-minded, schizophrenic or epileptic, were sterilized....
- Such people, said the out-of-sight narrator, were known variously as idiots, imbeciles or the feeble-minded, and lumped in together with the genuinely intellectually handicapped.
- After asking respondents their names, addresses, ages and occupations it asks them to list the state of their mental health reporting whether they are deaf and dumb, blind, lunatic, an imbecile or feeble-minded.
Derivatives
feeble-mindedly
- If the media were allowed to follow up, as opposed to being cold-bloodedly and feeble-mindedly suppressed, the whole petition phenomenon would have disappeared eight hundred years ago!
- Are the noise issues as bad as I have been feeble-mindedly led to believe?
- You can go on mischaracterizing the party as feeblemindedly as you want, but your party shall never, nor can ever, address these problems effectively.
feeble-mindedness
/ noun ...- He refers to ‘gullible consumers’ and goes on to argue that ‘today's average consumer may be an everyday victim of foolishness and feeble-mindedness in their consumption behaviour’.
- Even hardened journalists and academics, long resigned to their toil among the ignorant, have recoiled before the feeble-mindedness of the man.
- Similarly, his 'weasel' example makes it clear how much feeble-mindedness he assumes in his readership.