RhymeZone: trialist definitions

Definitions of trialist:

noun: An advocate of trialism, especially with reference to the proposed creation of a state comprising Austria, Hungary, and a Slavic region.
adjective: Involving three elements; especially, pertaining to a potential state comprising Austria, Hungary, and a Slavic region.
noun: (American spelling) A person who takes part in a trial (of a drug etc.)

(Definitions from Wiktionary)