to change from one substance into another; transmute.
2.
Theology. to change (the bread and wine) into the body and blood of Christ in the Eucharist.
Origin: 1400–50; v. use of late ME transsubstanciate (adj.) transubstantiated < ML trānssubstantiātus, ptp. of trānssubstantiāre.See trans-, substance, -ate1