10 letters · 19 points in Scrabble
noun retardation more severe than a moron but not as severe as an idiot
noun a stupid mistake
originFrom Middle English inbecillite, from Middle French imbecilité, imbecillité, and its etymon Classical Latin imbēcillitās. By surface analysis, imbecile + -ity.
Etymology from Wiktionary, CC BY-SA 3.0