Fitzwilliamite noun1 •A supporter of whig leader William Fitzwilliam, 4th Earl Fitzwilliam, especially his views on the need for parliamentary reform and Catholic emancipation.So Perrott's Irish friends learned that the Fitzwilliamites were formulating a charge against Perrott, with O'Rouane for chief witness. — 1908 formsFitzwilliamites
