fastness, swiftness, speed - a rate (usually rapid) at which something happens; "the project advanced with gratifying speed"

delay, postponement, time lag, wait, hold - time during which some action is awaited; "instant replay caused too long a delay"; "he ordered a hold in the action"

agent - an active and efficient cause; capable of producing a certain effect; "their research uncovered new disease agents"

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

delay, holdup - the act of delaying; inactivity resulting in something being put off until a later time