The Collaborative International Dictionary of English v.0.48:

Coptic Church \Coptic Church\
   The native church of Egypt or church of Alexandria, which in
   general organization and doctrines resembles the Roman
   Catholic Church, except that it holds to the Monophysitic
   doctrine which was condemned (a. d. 451) by the council of
   Chalcedon, and allows its priests to marry. The "pope and
   patriarch" has jurisdiction over the Abyssinian Church. Since
   the 7th century the Coptic Church has been so isolated from
   modifying influences that in many respects it is the most
   ancient monument of primitive Christian rites and ceremonies.
   But centuries of subjection to Moslem rule have weakened and
   degraded it.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

Coptic Church
    n 1: the ancient Christian church of Egypt