The Collaborative International Dictionary of English v.0.48:

Popery \Pop"er*y\, n.
   The religion of the Roman Catholic Church, comprehending
   doctrines and practices; -- generally used in an opprobrious
   sense.
   [1913 Webster]

WordNet (r) 3.0 (2006):

popery
    n 1: offensive terms for the practices and rituals of the Roman
         Catholic Church [syn: popery, papism]