English to English

noun (n)

• retardation more severe than a moron but not as severe as an idiot(noun.cognition)

  source: wordnet30
• a stupid mistake(noun.act)

  Synonym:
  betise, folly, foolishness, stupidity
  

  source: wordnet30
• The quality of being imbecile; weakness; feebleness, esp. of mind.(noun)

  source: webster1913