A muzzle is a device that is placed over the snout of an animal to keep them from biting or otherwise opening their mouth.
A muzzle typically consists of a small cage structure made of metal or some other sturdy material. This cage keeps the animal's mouth closed enough to prevent biting, and is secured to the animal's face via straps typically made of leather, though nylon straps have been observed.
Role in the Film
During Judy Hopps' first day at the ZPD, a muzzled wolf is seen being taken through the Police Department lobby by a tiger officer. The wolf protests through his muzzle that his opponent bared his teeth first, to which the officer rolls his eyes.
Near the middle of the film, Nick Wilde is telling Judy about his childhood and his desire to join the Zootopia Junior Ranger Scouts. During his "initiation", he is seized and muzzled by the other scouts, because he was a fox. After Nick runs outside, he hastily removes the muzzle, throwing it across the ground, and begins to cry. Later, during Judy’s press conference, still images of the savage mammals wearing muzzles are shown on the screen behind Judy, with expressions ranging from vicious to sad. This sight reminds Nick of his own traumatic experience, to the extent of triggering PTSD. Shortly after, he scolds Judy, who says that he's "not that kind of predator." Nick replies, "The kind that needs to be muzzled?"