(noun)
a person who is a part of the Communist Party, the single political party in the totalitarian government in the Soviet Union, which held an authoritarian rule and controlled the means of production;
e.g. They knew if a communist heard their complaints, they would be punished.
(noun)
a person who believes in the system or theory that supports goods being owned collectively and accessible to everyone as needed, rather than as private property;
e.g. He may be considered a communist because of his liberal beliefs.