Nouns

(n)gun muzzle, muzzlethe open circular discharging end of a gun
(n)muzzleforward projecting part of the head of certain animals; includes the jaws and nose
(n)muzzlea leather or wire restraint that fits over an animal's snout (especially a dog's nose and jaws) and prevents it from eating or biting
(n)gag, muzzlerestraint put into a person's mouth to prevent speaking or shouting

Verbs

(v)muzzlefit with a muzzle“muzzle the dog to prevent it from biting strangers”
(v)gag, muzzleprevent from speaking out“The press was gagged”
(v)gag, muzzletie a gag around someone's mouth in order to silence them“The burglars gagged the home owner and tied him to a chair”