Abstainer
Part of speech: noun
Definition: Agent noun of abstain; one who abstains; especially, one who abstains from something they enjoy, such as the use of intoxicating liquors.
Abstinent
Part of speech: adjective
Definition: Refraining from indulgence, especially from the indulgence of appetite; abstemious; continent; temperate. - Beaumont and Fletcher
Part of speech: noun
Definition: One who abstains.One of a sect who appeared in France and Spain in the 3d century.