A wrinkling of the forehead with the eyebrows brought together, typically indicating displeasure, severity, or concentration.

(Canada, US) A downturn of the corners of the mouth, typically expressing sadness.

(intransitive) To have a frown on one's face.

(intransitive, figurative) To manifest displeasure or disapprobation; to look with disfavour or threateningly.

(transitive) To repress or repel by expressing displeasure or disapproval; to rebuke with a look.

(transitive) To communicate by frowning.