stop somebody from expressing their opinion
muzzle - gag
The original use of the word ‘muzzle’ was to refer to a guard that covers an animal’s, particularly a dog’s, mouth to prevent it from biting others. The term has since been adapted to also describe the act of preventing a person or organization from speaking freely in public by figuratively putting a guard over their mouth. In this context, it is almost always used to express disapproval.
I’ve been told that for the sake of public relations, I should not to raise the issue with the CEO at the AGM. I can’t believe that my company would try to muzzle me like that!
The government in that country have been muzzling journalists for years, using a combination of bribes and threats.
I could not talk about my firing until a certain period of time had elapsed as I was muzzled by a non-disclosure agreement.