The Collaborative International Dictionary
Impanation \Im"pa*na"tion\, n. [Cf. F. impanation. See Impanate, a.] (Eccl.) Embodiment in bread; the supposed real presence and union of Christ's material body and blood with the substance of the elements of the eucharist without a change in their nature; -- distinguished from transubstantiation, which supposes a miraculous change of the substance of the elements. It is akin to consubstantiation.
Wiktionary
n. (context Christianity English) The actual, substantial presence of the body of Christ with the bread and wine of the sacrament of the Lord's Supper — as opposed to transubstantiation.
Wikipedia
Impanation ( Latin, impanatio, "embodied in bread") is a high medieval theory of the real presence of the body of Jesus Christ in the consecrated bread of the Eucharist that does not imply a change in the substance of either the bread or the body. This doctrine, apparently patterned after Christ's Incarnation (God is made flesh in the Person of Jesus Christ), is the assertion that "God is made bread" in the Eucharist. Christ's divine attributes are shared by the eucharistic bread via his body. This view is similar but not identical to the theory of consubstantiation associated with Lollardy. It is considered a heresy by the Roman Catholic Church and is also rejected by classical Lutheranism. Rupert of Deutz (d. 1129) and John of Paris (d. 1306) were believed to have taught this doctrine.