The Collaborative International Dictionary of English v.0.48:

Byzantinism \Byzantinism\ n.
   The doctrine that the state is supreme over the church in
   ecclesiastical matters.

   Syn: Erastianism, Caesaropapism.
        [WordNet 1.5]

WordNet (r) 3.0 (2006):

Byzantinism
    n 1: the doctrine that the state is supreme over the church in
         ecclesiastical matters [syn: Erastianism, Byzantinism,
         Caesaropapism]