[UK] Constitutionalist was a label used by some British politicians standing for parliament in the 1920s, instead of the more traditional party labels. The label was used primarily by former supporters of the David Lloyd George led Coalition Government, and most notably by Winston Churchill. However, there was no actual party called the Con...
• (n.) One who advocates a constitutional form of government; a constitutionalist.
Con`sti·tu'tion·al·ist noun One who advocates a constitutional form of government; a constitutionalist. 
[n] - an advocate of constitutional government
noun an advocate of constitutional government
an adherent or advocate of constitutionalism or of an existing constitution. · an expert on a political constitution.