stupidity - a poor ability to understand or to profit from experience

mental defectiveness, abnormality - retardation sufficient to fall outside the normal range of intelligence

mental deficiency, moronity - mild mental retardation

amentia, idiocy - extreme mental retardation

imbecility - retardation more severe than a moron but not as severe as an idiot

Down syndrome, Down's syndrome, mongolianism, mongolism, trisomy 21 - a congenital disorder caused by having an extra 21st chromosome; results in a flat face and short stature and mental retardation