Mentally affected or weak. Also: morbid, enjoying sick humour (see sense A. 7f). Now rare.

Lacking sense or judgement; foolish; crazy; (also) having one's mental faculties impaired in old age. Cf. dottled, adj.

Of an action, attribute, idea, etc.: characterized by or indicating foolishness or stupidity; (now usually) exhibiting a decline of mental faculties…

Foolish, stupid, silly; lacking sense or judgement; having one's mental faculties impaired, esp. by old age.

Originally and chiefly Scottish. Mentally impaired or retarded.

Foolish; of impaired intellect or understanding. Now rare (English regional (Yorkshire) in later use).

colloquial. Lacking intelligence or common sense; easily imposed on or deceived; foolish, silly. Also: mentally ill; having learning…

Feeble (in one's intellect, the brain, head, etc.).

Slightly mad, crazy, or mentally unsound; a little eccentric. Chiefly in predicative use. Frequently in phrases, as touched in the head, touched in…

Confused, befuddled.

Of a person: having a physical or mental disability. Now historical and offensive.

Chiefly Scottish, Irish English (northern), and English regional (northern and north midlands). Having a low learning ability or intellectual…

figurative and in figurative contexts. colloquial and regional. Of a person: lacking in intelligence or common sense; half-witted, stupid, foolish…

Of a person: mentally confused, esp. in old age; eccentric, slightly mad. Also of ideas, behaviour, etc.: ridiculous, absurd.

figurative. Halting; feeble.

that dodders; now frequently mentally feeble or inept; futile, footling.

Mentally deficient; half-witted.

British colloquial. ninepence in (also to) the shilling: below average, esp. in intelligence; mentally slow. Also as n.: a person of low intelligence.

= balmy, adj. 7 (of which it is an altered form, after barm, n.2). slang.

Drivelling, sloppily sentimental; having the characteristics of a ‘drip’ (see drip, n. 3c); ‘wet’. colloquial (originally U.S.).

Stupid, feeble-minded; worthless; contemptible.