"imbecility" in the noun sense
1. imbecility
retardation more severe than a moron but not as severe as an idiot
2. stupidity, betise, folly, foolishness, imbecility
a stupid mistake
Source: WordNet® (An amazing lexical database of English)
Princeton University "About WordNet®."
WordNet®. Princeton University. 2010.
View WordNet® License