http://dictionary.reference.com/browse/christian
How can one have a Christian faith until such time as there was a christian Church?
Chris‧tian Âadjective 1. of, pertaining to, or derived from Jesus Christ or His teachings: a Christian faith.
Peter was Christian when Jesus Christ called him the Rock upon which He would build His Church.
You're hoist on your own petard by the dictionary reference you gave. You must be getting tired.