What does the word frown mean?

Usage examples for frown

  1. Lord Probus followed with a frown. – The Squire's Daughter by Silas K(itto) Hocking
  2. His hard and somewhat cruel mouth was tightly closed; there was a slight frown upon his forehead. – The Great Impersonation by E. Phillips Oppenheim
  3. Now when I looked the frown had left his brow. – Darrel of the Blessed Isles by Irving Bacheller