n.
  - the projecting part of the face, including the nose and mouth, of an animal such as a dog or horse. ▸a guard fitted over an animal's muzzle to stop it biting or feeding. 
- the open end of the barrel of a firearm.
v.
  - put a muzzle on (an animal).
- prevent from freedom of expression.
Etymology
  ME: from OFr. musel, dimin. of med. L. musum.