Someone deranged and possibly dangerous.

synonyms: looney, loony, nutcase, weirdo.

Roget 504: madman, lunatic, maniac, bedlamite^†, candidate for Bedlam, raver^†, madcap, crazy; energumen^†; automaniac^†, monomaniac, dipsomaniac, kleptomaniac; hypochondriac etc. (low spirits);; crank, Tom o'Bedlam.    dreamer etc. 515; rhapsodist, seer, highflier^†, enthusiast, fanatic, fanatico [Sp.]; exalte [Fr.]; knight errant, Don Quixote.    idiot etc. 501.    ... show more

Dutch: oelewapper, koekert
Polish: obłąkaniec, chory na głowę, pomyleniec, pomylony, nienormalny, szaleniec, wariat

Affected with madness or insanity.

synonyms: brainsick, demented, disturbed, mad, sick, unbalanced, unhinged.

Roget 160: weak, feeble, debile^†; impotent etc. 158; relaxed, unnerved, etc. v.; sapless, strengthless^†, powerless; weakly, unstrung, flaccid, adynamic^†, asthenic^†; nervous.    soft, effeminate, feminate^†, womanly.    frail, fragile, shattery^†; flimsy, unsubstantial, insubstantial, gimcrack, gingerbread; rickety, creaky, creaking, cranky; craichy^†; drooping, tottering etc. v.. broken, lame, withered, shattered, shaken, crazy, shaky; palsied etc. 158; decrepit.    languid, poor, infirm; faint, faintish^†; sickly etc. (disease) 655; dull, slack, evanid^†, spent, short-winded, effete; weather-beaten; decayed, rotten, worn, seedy, languishing, wasted, washy, laid low, pulled down, the worse for wear.    unstrengthened etc. 159^†, unsupported, unaided, unassisted; aidless^†, defenseless etc. 158; cantilevered (support) 215.    on its last legs; weak as a child, weak as a baby, weak as a chicken, weak as a cat, weak as a rat; weak as water, weak as water gruel, weak as gingerbread, weak as milk and water; colorless etc. 429.    ... show more

Roget 503: insane, mad, lunatic, loony [Coll.]; crazy, crazed, aliene^†, non compos mentis; not right, cracked, touched; bereft of reason; all possessed, unhinged, unsettled in one's mind; insensate, reasonless, beside oneself, demented, daft; phrenzied^†, frenzied, frenetic; possessed, possessed with a devil; deranged, maddened, moonstruck; shatterpated^†; mad-brained, scatter brained, shatter brained, crackbrained; touched, tetched [Coll.]; off one's head.    [behavior suggesting insanity] maniacal; delirious, lightheaded, incoherent, rambling, doting, wandering; frantic, raving, stark staring mad, stark raving mad, wild-eyed, berserk; delusional, hallucinatory.    [behavior somewhat resembling insanity] corybantic^†, dithyrambic; rabid, giddy, vertiginous, wild; haggard, mazed; flighty; distracted, distraught; depressed; agitated, hyped up; bewildered etc. (uncertain) 475.    mad as a March hare, mad as a hatter; of unsound mind etc. n.; touched in one's head, wrong in one's head, not right in one's head, not in one's right mind, not right in one's wits, upper story; out of one's mind, out of one's wits, out of one's skull [Coll.], far gone, out of one's senses, out of one's wits; not in one's right mind.    fanatical, infatuated, odd, eccentric; hypped^†, hyppish^†; spaced out [Coll.].    imbecile, silly, etc. 499.    ... show more

Foolish; totally unsound:
— A crazy scheme.

synonyms: half-baked, screwball, softheaded.

Possessed by inordinate excitement.

Bizarre or fantastic.

Intensely enthusiastic about or preoccupied with:
— Crazy about cars and racing.

synonyms: dotty, gaga, wild.