[fol.ly] n, pl follies [ME folie, fr. OF, fr. fol fool] (13c) 1: lack of good sense or normal prudence and foresight
2. a: criminally or tragically foolish actions or conduct b obs: evil, wickedness; esp: lewd behavior
3: a foolish act or idea
4: an excessively costly or unprofitable undertaking
5: an often extravagant picturesque building erected to suit a fanciful taste