The Collaborative International Dictionary of English v.0.48:

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.
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   2. A foolish act; an inconsiderate or thoughtless procedure;
      weak or light-minded conduct; foolery.
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            What folly 'tis to hazard life for ill. --Shak.
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   3. Scandalous crime; sin; specifically, as applied to a
      woman, wantonness.
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            [Achan] wrought folly in Israel.      --Josh. vii.
                                                  15.
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            When lovely woman stoops to folly.    --Goldsmith.
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   4. The result of a foolish action or enterprise.
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            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.
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WordNet (r) 3.0 (2006):

follies
    n 1: a revue with elaborate costuming