Source : Webster's Revised Unabridged Dictionary (1913)

Scowl \Scowl\ (skoul), v. i. [imp. & p. p. {Scowled} (skould);
   p. pr. & vb. n. {Scowling}.] [Akin to Dan. skule; cf. Icel.
   skolla to skulk, LG. schulen to hide one's self, D. schuilen,
   G. schielen to squint, Dan. skele, Sw. skela, AS. sceolh
   squinting. Cf. {Skulk}.]
   1. To wrinkle the brows, as in frowning or displeasure; to
      put on a frowning look; to look sour, sullen, severe, or
      angry.

            She scowled and frowned with froward countenance.
                                                  --Spenser.

   2. Hence, to look gloomy, dark, or threatening; to lower.
      ``The scowling heavens.'' --Thomson.

Scowl \Scowl\, v. t.
   1. To look at or repel with a scowl or a frown. --Milton.

   2. To express by a scowl; as, to scowl defiance.

Scowl \Scowl\, n.
   1. The wrinkling of the brows or face in frowing; the
      expression of displeasure, sullenness, or discontent in
      the countenance; an angry frown.

            With solemn phiz, and critic scowl.   --Lloyd.

   2. Hence, gloom; dark or threatening aspect. --Burns.

            A ruddy storm, whose scowl Made heaven's radiant
            face look foul.                       --Crashaw.

Source : WordNet®

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