Chapter Words Relating to the Intellectual Faculties of Index by Roget's Thesaurus

To render, or drive mad; to madden, dementate, turn the brain, addle the wits, turn one's head, befool, infatuate, craze.

(Adjectives). Insane, mad, lunatic, crazy, crazed, non compos, cracked, cranky, of unsound or abnormal mind, touched, deficient, out of one's mind, off one's head or nut, bereft of reason, unsettled in one's mind, unhinged, insensate, reasonless, beside oneself, demented, daft, dotty, possessed, maddened, moonstruck, mad-brained, maniacal, delirious, incoherent, rambling, doting, doited, wandering, frantic, phrenetic, paranoiac, raving, corybantic, dithyrambic, rabid, light-headed, giddy, vertiginous, wild, haggard, flighty, distracted, distraught, hag-ridden, écervelé, tête montée.

(Phrases). The head being turned; having a bee in one's bonnet; far gone; stark staring mad; mad as a March hare; the devil being in one; dizzy as a goose; candidate for Bedlam; like one possessed.

The wits going wool-gathering, or bird's-nesting.

480. Madman (Substantives), lunatic, maniac, bedlamite, energumen, raver, monomaniac, dreamer, visionary, a high-flier, madcap, megalomaniac, psychopath, malade imaginaire, crank, mèand.