/fol"ee/ , n. , pl. follies for 2-6.
1. the state or quality of being foolish; lack of understanding or sense.
2. a foolish action, practice, idea, etc.; absurdity: the folly of performing without a rehearsal.
3. a costly and foolish undertaking; unwise investment or expenditure.
4. Archit. a whimsical or extravagant structure built to serve as a conversation piece, lend interest to a view, commemorate a person or event, etc.: found esp. in England in the 18th century.
5. follies , a theatrical revue.
6. Obs. wickedness; wantonness.
[ 1175-1225; ME folie fol, fou foolish, mad. See FOOL 1 ]
Syn. 2. imprudence, rashness, mistake, foolishness, indiscretion, injudiciousness; madness, lunacy.