Mentally deficient or deranged; out of one's wits, crazy, lunatic. †Also, stupefied, dazed.

Mad, deranged; deficient in understanding or intellect. Also: dazed, confused. Now English regional (northern and north-east midlands).

Insane, mad; diseased or impaired in mind. Obsolete.

Foolish, crazy; having one's mental faculties impaired, esp. by old age.

Not having all his or her wits; weak-minded; daft.

That is in a state of dementia or imbecility; idiotic. Now rare except in Scots Law.

(a) a mild eccentricity or mental disturbance in a person; something wrong in one's way of thinking; frequently in to have a screw loose; †(b)…

Having the mental powers impaired. lost of wits: imbecile (cf. dialect use of lost in this sense).

‘Soft’, weak-minded, idiotic. Also as n. (see quot. 1903). See also barmy, adj. slang.

figurative phr. (originally Australian colloquial). a shingle short: ‘a tile loose’: said of one who is mentally deficient.

Of or designating a retardate. Also (derogatory slang): stupid, idiotic. Cf. retarded, adj. 2.

colloquial. Mentally ill; mentally disabled. Also in weakened sense: irrational, uncontrolled, eccentric, crazy.

Psychology. Characterized by low intelligence; spec. characterized by a (mild) mental disability caused by genetic or environmental factors…

colloquial. = mental, adj.1 6.