Parliamentarian

A member of a parliament, congress or an elected national legislative body of another name.

A person well-versed in parliamentary procedure.

An officer in most legislative bodies charged with being well-versed in the parliamentary rules of that legislative house, and whose rulings are taken as authoritative, to be appealed only to the whole of the house itself under special rules.

Of or relating to a parliament; favouring the establishment of a parliament.

"a parliamentarian democracy; the parliamentarian movement"

Of or relating to the Parliamentarians (supporters of the parliament during the English Civil War (1642–1651)).