Yes, muzzle is a Scrabble word!

Verb

1. Fit with a muzzle

2. Prevent from speaking out

3. Tie a gag around someone's mouth in order to silence them

Noun

1. The open circular discharging end of a gun

2. Forward projecting part of the head of certain animals; includes the jaws and nose

3. A 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

4. Restraint put into a person's mouth to prevent speaking or shouting