1. The projecting part of an animal's face, made up of its nose and jaws: One example of a muzzler is a device prevents it from opening its mouth in order to keep it from biting, barking, or eating.
2. The front open end of the barrel of a firearm.
3. Something that is meant to prevent free expression: To muzzle the press when reporting on a military operation.
4. Etymology: from Middle English mosel, from Old French musel, from Medieval Latin musellum, diminutive of musum, "muzzle, snout".