Definition of Folly:

nonsense, ridiculous idea

Synonyms of Folly:

madness, silliness, craziness, absurdity, indiscretion, foolishness, recklessness, idiocy, stupidity, lunacy, inanity, fatuity, vice, unsoundness, triviality, imprudence, imbecility, impracticality, irrationality, senselessness, rashness, preposterousness, inadvisability, daftness, obliquity, dottiness, dumb thing to do, dumb trick, witlessness

Opposite/Antonyms of Folly:

understanding, seriousness, judgment, intelligence, carefulness, care, sense, wisdom, knowledge

Sentence/Example of Folly: