The Collaborative International Dictionary of English v.0.48:

Frown \Frown\ (froun), v. i. [imp. & p. p. Frowned (fround);
   p. pr. & vb. n. Frowning.] [OF. froignier, F. frogner, in
   se refrogner, se renfrogner, to knit the brow, to frown;
   perh. of Teutonic origin; cf. It. in frigno wrinkled,
   frowning, Prov. It. frignare to cringe the face, to make a
   wry face, dial. Sw. fryna to make a wry face,]
   1. To contract the brow in displeasure, severity, or
      sternness; to scowl; to put on a stern, grim, or surly
      look.
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            The frowning wrinkle of her brow.     --Shak.
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   2. To manifest displeasure or disapprobation; to look with
      disfavor or threateningly; to lower; as, polite society
      frowns upon rudeness.
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            The sky doth frown and lower upon our army. --Shak.
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