The Collaborative International Dictionary of English v.0.48:

Episcopalian \E*pis`co*pa"li*an\, a.
   Pertaining to bishops, or government by bishops; episcopal;
   specifically, of or relating to the Protestant Episcopal
   Church.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Episcopalian \E*pis`co*pa"li*an\, n.
   One who belongs to an episcopal church, or adheres to the
   episcopal form of church government and discipline; a
   churchman; specifically, in the United States, a member of
   the Protestant Episcopal Church.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Episcopalian
    adj 1: of or pertaining to or characteristic of the Episcopal
           church; "the Episcopal hierarchy"; "married by an
           Episcopalian minister" [syn: Episcopal, Episcopalian]
    n 1: a member of the Episcopal church