Definition of Foolishness
Noun
fool·ish·ness (source)
1. The state or quality of being foolish; lack of good sense or judgement.
2. The act or instance of doing something irrational, senseless, or absurd.
Synonyms:
stupidity, absurdity, silliness, idiocy, nonsense, folly, imprudence, recklessness, tomfoolery
Antonyms:
wisdom, prudence, intelligence, sense, rationality