foolishness

/ˈfulɪʃnəs/
noun
  1. Behavior or actions that show a lack of good sense or judgment; stupidity.
    • His foolishness in spending all his money on lottery tickets left him broke.
    • The teacher warned the students about the foolishness of cheating on the exam.
    • Looking back, I can see the foolishness of my decision to quit school.
  2. A silly or unwise act, idea, or statement.
    • She laughed at the foolishness of the rumor spreading around town.
    • Don't listen to his foolishness about aliens living on the moon.
    • The meeting was full of foolishness and no one took it seriously.
Antonyms