Insane or mentally ill. / Suffering from dementia. / (informal) Crazy; ridiculous.

simple past tense and past participle of dement

(obsolete) insane, demented

An insane person, or one afflicted with dementia

(transitive) To drive mad; to craze

(obsolete) To dement, to make crazy.

(obsolete) Deprived of reason.

Third-person singular simple present indicative form of dement

Causing dementia. / Undergoing dementia.

(archaic) The act of depriving of reason; madness.