From the Lutheran Confessions:
"We believe, teach, and confess that the body and blood of Christ are received with the bread and wine, not only spiritually by faith, but also orally; yet not in a Capernaitic, but in a supernatural, heavenly mode, because of the sacramental union;" - Epitome of the Formula of Concord, Article VII, 15
The key word here is "Capernaitic". A word that might at first seem confusing, but it refers to situation which took place in Capernaum as recorded in John chapter 6. Here Christ says that whoever eats His flesh and drinks His blood shall have everlasting life, it was at this point that many turned away for this was a "hard saying". Thus here Capernaitic refers to the idea that the consuming of Christ's flesh and blood is a cannibalistic act.
We are not sawing off a chunk of Christ's flesh from a limb and consuming it; that is simply not what we, or any Christian down through the ages, has believed. But rather our confession is that Jesus Christ is truly bodily present here "in and under" these elements of bread and wine, and thus whoever partakes of these partakes not of mere bread and wine, but of the very flesh and blood of Christ.
Those who would charge us with cannibalism are like those who turned away from Christ; but we must instead be like those who remained, knowing that His word is our hope and salvation. And so when He says this bread is His flesh, and this wine is His blood we are beholden, by faith, to receive these very things as what He says they are. And so we receive very Jesus Christ here, in and under, these meager signs of bread and wine; not a symbol of Him, not a figure of Him, but He Himself, the very Son of God who became flesh, suffered, died, was buried, and rose again. It is this very Jesus which we meet and receive here in His Supper, in the fullness of Himself, the one God-Man, body, soul, and divinity: Jesus Christ our Lord.
-CryptoLutheran