Concise Oxford English Dictionary
muzzle
■ noun
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.
■ verb
put a muzzle on (an animal).
prevent from freedom of expression.

ME: from OFr. musel, dimin. of med. L. musum.
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Concise Oxford Thesaurus
muzzle
▶ noun the dog’s velvety muzzle: SNOUT, nose, mouth, maw.
▶ verb attempts to muzzle the media: GAG, silence, censor, stifle, restrain, check, curb, fetter.
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Merriam-Webster Collegiate® Dictionary
1muz·zle
Pronunciation: ‘mə-zəl
Function: noun
Etymology: Middle English mosel, from Middle French musel, from Old French *mus mouth of an animal, from Medieval Latin musus
Date: 15th century

1 : the projecting jaws and nose of an animal : SNOUT
2 a : a fastening or covering for the mouth of an animal used to prevent eating or biting b : something (as censorship) that restrains normal expression
3 : the open end of an implement especially : the discharging end of a weapon

muzzle[1] 2muzzle
Function: transitive verb
Inflected Form: muz·zled ; muz·zling \’məz-liŋ, ‘mə-zə-\
Date: 15th century

1 : to fit with a muzzle
2 a : GAG b : RESTRAIN, RESTRICT –muz·zler \-lər\ noun

Synonyms

agreeable, blessed (also blest), darling, delectable, delicious, delightful, delightsome, dreamy, dulcet, enjoyable, felicitous, good, grateful, gratifying, heavenly, jolly, luscious, nice, palatable, pleasant, pleasing, pleasurable, pretty, satisfying, savory (also savoury), sweet, tasty, welcome

Antonyms

disagreeable, pleasureless, unpalatable, unpleasant, unwelcome

Source: Congenial | Definition of Congenial by Merriam-Webster