Imbecility(n.) The quality of being imbecile; weakness; feebleness, esp. of mind.
Thesaurus Entries
amentia, arrested development, asininity, backwardness, battiness, blithering idiocy, brainlessness, buffoonery, clownishness, crackpottedness, crankiness, craziness, cretinism, daffiness, desipience, disability, disablement, disqualification, eccentricity, fatuity, fatuousness, folly, foolery, foolheadedness, foolishness, frivolity, frivolousness, giddiness, goofiness, half-wittedness, idiocy, idiotism, inability, inadequacy, inanity, incapability, incapacitation, incapacity, incompetence, incompetency, inefficiency, ineptitude, infancy, infantilism, inferiority, insanity, insufficiency, legal incapacity, lunacy, madness, mental defectiveness, mental deficiency, mental handicap, mental retardation, mindlessness, minority, mongolianism, mongolism, mongoloid idiocy, moronism, moronity, niaiserie, nugacity, nuttiness, profound idiocy, queerness, retardation, retardment, sappiness, screwiness, senselessness, silliness, simple-wittedness, simplemindedness, simpleness, simplicity, stupidity, subnormality, thoughtlessness, triflingness, triviality, unfitness, wackiness, wardship, weirdness, witlessness, zaniness, zanyism