Transubstantiation

Transubstantiation, the doctrine of Roman Catholics as defined by the Council of Trent, that the bread and wine of the Eucharist is, after consecration by a priest, converted mystically into the body and blood of Christ, and is known as the docrine of the Real Presence.

Definition taken from The Nuttall Encyclopædia, edited by the Reverend James Wood (1907)