|1.||(esp in Roman Catholic theology)|
|a. the doctrine that the whole substance of the bread and wine changes into the substance of the body and blood of Christ when consecrated in the Eucharist|
|b. Compare consubstantiation the mystical process by which this is believed to take place during consecration|
|2.||a substantial change; transmutation|
According to the traditional teaching of the Roman Catholic Church, the presence of Jesus in the sacrament of Communion. Through transubstantiation, the bread and wine consumed by worshipers become the body and blood of Jesus when a priest, acting on Jesus' behalf, speaks the words “This is my body” and “This is my blood” over them.
Note: Transubstantiation was the focus of a great controversy during the Reformation, because most other groups of Christians do not maintain this doctrine. They usually hold that the body and blood of Jesus are only symbolically present in the bread and wine or that the bread and wine are the body and blood of Jesus and bread and wine at the same time.