Source : Webster's Revised Unabridged Dictionary (1913)

Protestantism \Prot"es*tant*ism\, n. [Cf. F. protestantisme.]
   The quality or state of being protestant, especially against
   the Roman Catholic Church; the principles or religion of the
   Protestants.

Source : WordNet®

Protestantism
     n : the theological system of any of the churches of western
         Christendom that separated from the Roman Catholic Church
         during the Reformation