Folly \Fol"ly\, n.; pl. Follies. [OE. folie, foli, F. folie, fr. fol, fou, foolish, mad. See Fool.]

1. The state of being foolish; want of good sense; levity, weakness, or derangement of mind.

2. A foolish act; an inconsiderate or thoughtless procedure; weak or light-minded conduct; foolery.

What folly 'tis to hazard life for ill. --Shak.

3. Scandalous crime; sin; specifically, as applied to a woman, wantonness.

[Achan] wrought folly in Israel. --Josh. vii. 15.

When lovely woman stoops to folly. --Goldsmith.

4. The result of a foolish action or enterprise.

It is called this man's or that man's ``folly,'' and name of the foolish builder is thus kept alive for long after years. --Trench.

Source: Webster's Revised Unabridged Dictionary (1913)