Noun

1. The wrinkling of the brows or face in frowning; the expression of displeasure, sullenness, or discontent in the countenance; an angry frown.
2. Hence, gloom; dark or threatening aspect.

Verb

1. To wrinkle the brows, as in frowning or displeasure; to put on a frowning look; to look sour, sullen, severe, or angry.
2. Hence, to look gloomy, dark, or threatening; to lower.
3. To look at or repel with a scowl or a frown.
4. To express by a scowl; as, to scowl defiance.