A moue is a grimace you make with your lips. If you make this expression, you're usually showing distaste, petulance, or a similar emotion. Moue is also used, however, to refer to a flirtatious pout.
The word moue is pronounced "moo," like the sound a cow makes, although the origin of the word has nothing to do with cows. Instead, the noun moue comes from the Middle Dutch word mouwe, which meant a protruding lip. You can make a moue of displeasure when someone steals your parking spot or give a coy moue when you're trying to get away with something. Either way, you're pouting.