A person who practices or believes in abstentionism, refusing to participate in something as a matter of principle.
From 'abstentionism' plus the agent suffix '-ist' (one who practices), creating a term for individuals committed to systematic non-participation, documented since the 19th century.
The term 'abstentionist' became famous in Irish history when Sinn Féin members elected to Westminster refused to attend Parliament in the 1920s, treating their opposition as so fundamental they wouldn't even show up to argue against it.
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