Source : Webster's Revised Unabridged Dictionary (1913)

Frown \Frown\, v. i. [imp. &, p. p. {Frowned}; 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.

            The frowning wrinkle of her brow.     --Shak.

   2. To manifest displeasure or disapprobation; to look with
      disfavor or threateningly; to lower; as, polite society
      frowns upon rudeness.

            The sky doth frown and lower upon our army. --Shak.

Frown \Frown\, v. t.
   To repress or repel by expressing displeasure or disapproval;
   to rebuke with a look; as, frown the impudent fellow into
   silence.

Frown \Frown\, n.
   1. A wrinkling of the face in displeasure, rebuke, etc.; a
      sour, severe, or stere look; a scowl.

            His front yet threatens, and his frowns command.
                                                  --Prior.

            Her very frowns are fairer far Than smiles of other
            maidens are.                          --H.
                                                  Coleridge.

   2. Any expression of displeasure; as, the frowns of
      Providence; the frowns of Fortune.

Source : WordNet®

frown
     n : a facial expression of dislike or displeasure [syn: {scowl}]

frown
     v : look angry or sullen, wrinkle one's forehead, as if to
         signal disapproval [syn: {glower}, {lour}, {lower}]