(adjective)
relating to or resembling the members of the political party that seized control of Russia in 1917 during a revolution and then became the Communist Party, or the beliefs or policies of this party;
e.g. The country was under by Bolshevik control for years.
(noun)
(derogatory) broadly, a person who holds revolutionary political views, typically in terms of favoring radical reform;
e.g. They refused to listen to anything a Bolshevik had to say.