Dissident (noun)

1. A person who opposes the official policy, ideology, or government of their country, especially a communist country.
2. A person who disagrees with the established beliefs or practices of a group or organization.

Origin:

Mid 17th century: from latin dissident- "differing", from the verb dissidentare, from dis- (expressing negation) + sidentare "to be of the same mind".

Examples:

1. He was arrested for being a dissident against the government.
2. The dissident group was advocating for democratic reforms.
3. She was a dissident voice in the party.
4. The dissident movement was suppressed by the government.
5. The dissident was exiled for his political views.