Change (the Eucharist bread and wine) into the body and blood of Christ.
2.
Change or alter in form, appearance, or nature. Synonyms:transform, transmute."She transformed the clay into a beautiful sculpture" , "Transubstantiate one element into another"
... matter of life. A singular inward laboratory, which I possess, will dissolve a certain portion of the modified protoplasm; the solution so formed will pass into my veins; and the subtle influences to which it will then be subjected will convert the dead protoplasm into living protoplasm, and transubstantiate... — Lay Sermons, Addresses and Reviews • Thomas Henry Huxley