The noun countenance means the face or its expression. If you're a great poker player, you probably have a calm countenance.
Countenance comes from a French word for "behavior," but it has become a fancy term for either the expression of a face or the face itself: "He had a puzzled countenance," or "what a charming countenance!" Countenance can also be a verb meaning to tolerate or approve. If someone does something offensive, tell them, "I'm afraid I can't countenance that."