Retardation more severe than a moron but not as severe as an idiot.

Roget 158: impotence; inability, disability; disablement, impuissance, imbecility; incapacity, incapability; inaptitude, ineptitude, incompetence, unproductivity^†; indocility^†; invalidity, disqualification; inefficiency, wastefulness.    telum imbelle [Lat.], brutum fulmen [Lat.], blank, blank cartridge, flash in the pan, vox et proeterea nihil [Lat.], dead letter, bit of waste paper, dummy; paper tiger; Quaker gun.    inefficacy etc. (inutility) 645^†; failure etc. 732.    helplessness etc. adj.; prostration, paralysis, palsy, apoplexy, syncope, sideration^†, deliquium [Lat.], collapse, exhaustion, softening of the brain, inanition; emasculation, orchiotomy [Med.], orchotomy [Med.].    cripple, old woman, muff, powder puff, creampuff, pussycat, wimp, mollycoddle; eunuch.    ... show more

Roget 450a: absence of intellect, want of intellect etc. 450; imbecility etc. 499.    brutality, brute force.    instinct, brute instinct, stimulus-response loop, conditioned response, instinctive reaction, Pavlovian response.    mimicry, aping (imitation) 19.    moron, imbecile, idiot; fool etc. 501; dumb animal; vegetable, brain dead.    ... show more

Polish: głuptactwo, imbecylizm

A stupid mistake.

synonyms: betise, folly, foolishness, stupidity.

Roget 497: absurdity, absurdness etc. adj.; imbecility etc. 499; alogy^†, nonsense, utter nonsense; paradox, inconsistency; stultiloquy^†, stultiloquence^†; nugacity^†.    blunder, muddle, bull; Irishism^†, Hibernicism^†; slipslop^†; anticlimax, bathos; sophism etc. 477.    farce, galimathias^†, amphigouri^†, rhapsody; farrago etc. (disorder) 59; betise [Fr.]; extravagance, romance; sciamachy^†.    sell, pun, verbal quibble, macaronic^†.    jargon, fustian, twaddle, gibberish etc. (no meaning) 517; exaggeration etc. 549; moonshine, stuff; mare's nest, quibble, self-delusion.    vagary, tomfoolery, poppycock, mummery, monkey trick, boutade [Fr.], escapade.    ... show more

Roget 499: want of intelligence etc. 498, want of intellect etc. 450; shadowness^†, silliness, foolishness etc. adj.; imbecility, incapacity, vacancy of mind, poverty of intellect, weakness of intellect, clouded perception, poor head, apartments to let; stupidity, stolidity; hebetude^†, dull understanding, meanest capacity, shortsightedness; incompetence etc. (unskillfulness) 699.    one's weak side, not one's strong point; bias etc. 481; infatuation etc. (insanity) 503.    simplicity, puerility, babyhood; dotage, anility^†, second childishness, fatuity; idiocy, idiotism^†; driveling.    folly, frivolity, irrationality, trifling, ineptitude, nugacity^†, inconsistency, lip wisdom, conceit; sophistry etc. 477; giddiness etc. (inattention) 458; eccentricity etc. 503; extravagance etc. (absurdity) 497; rashness etc. 863.    act of folly etc. 699.    ... show more

Dutch: imbeciliteit