Rigorist

noun

1. A person of strict or rigid principles or manners; in general, one who adheres to severity or purity in anything, as in style.
2. One who maintained the doctrine of rigorism: a term sometimes applied to Jansenists. Also tutiorist.
3. Characterized by strictness or severity in principles or practice; rigid; strict; exacting.
4. Specifically, pertaining to rigorism in theology: as, rigorist doctrines.
5. One who is rigorous; -- sometimes applied to an extreme Jansenist.