The Collaborative International Dictionary of English v.0.48:

Parliamentarian \Par`lia*men*ta"ri*an\, a.
   Of or pertaining to Parliament. --Wood.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Parliamentarian \Par`lia*men*ta"ri*an\, n.
   1. (Eng. Hist.) One who adhered to the Parliament, in
      opposition to King Charles I. --Walpole.
      [1913 Webster]

   2. One versed in the rules and usages of Parliament or
      similar deliberative assemblies; as, an accomplished
      parliamentarian.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Parliamentarian
    n 1: an elected member of the British Parliament: a member of
         the House of Commons [syn: Parliamentarian, Member of
         Parliament]
    2: an expert in parliamentary rules and procedures