A kisser is a casual, slightly old-fashioned slang term for someone's mouth or face. If someone says “He got punched right in the kisser,” they mean he got hit in the mouth or face.

You might hear this word in old movies or comic books, where a tough-talking character says something like “Wipe that smile off your kisser!” It has a joking, informal feeling to it, like calling your stomach a “belly” instead of using more formal words. While people don't use kisser as commonly today as they did fifty or seventy years ago, you'll still encounter it in stories set in earlier times or when someone's trying to sound playful or deliberately old-timey.

The word can also literally mean a person who kisses, though this meaning is less common and usually comes up only in specific contexts.