Jesus says “flesh” 21 times in the Gospels and the word flesh is used much more often in the whole Bible, It means, man, body
when St Paul said he had a torn in his flesh he didn’t mean a sliver of wood.
eat means to consume, to take in,
Instead of selectively defining hsi words, lets look at the actual passage:
51I am the living bread that came down from heaven; whoever eats this bread will live forever; and the bread that I will give is my flesh for the life of the world.”
52The Jews quarreled among themselves, saying, “How can this man give us [his] flesh to eat?”
53Jesus said to them, “Amen, amen, I say to you, unless you eat the flesh of the Son of Man and drink his blood, you do not have life within you.
54Whoever eats* my flesh and drinks my blood has eternal life, and I will raise him on the last day.
55For my flesh is true food, and my blood is true drink.
56Whoever eats my flesh and drinks my blood remains in me and I in him.
57Just as the living Father sent me and I have life because of the Father, so also the one who feeds on me will have life because of me.
58This is the bread that came down from heaven. Unlike your ancestors who ate and still died, whoever eats this bread will live forever.”
59These things he said while teaching in the synagogue in Capernaum.
The Words of Eternal Life.*
60Then many of his disciples who were listening said, “This saying is hard; who can accept it?”
61Since Jesus knew that his disciples were murmuring about this, he said to them, “Does this shock you?
62What if you were to see the Son of Man ascending to where he was before?*
63It is the spirit that gives life, while the flesh* is of no avail. The words I have spoken to you are spirit and life.
64But there are some of you who do not believe.” Jesus knew from the beginning the ones who would not believe and the one who would betray him.
65And he said, “For this reason I have told you that no one can come to me unless it is granted him by my Father.”
66As a result of this, many [of] his disciples returned to their former way of life and no longer accompanied him.
67Jesus then said to the Twelve, “Do you also want to leave?”
68Simon Peter answered him, “Master, to whom shall we go? You have the words of eternal life.
69We have come to believe and are convinced that you are the Holy One of God.”
So it appears that many of Jesus’s original disciples had the same reaction as you did: it was too hard for them to have faith in what he said because they did not understand how he could give them his flesh to eat and his blood to drink. And they left. They would never had left if they thought he was just speaking figuratively, now would they. They never left when he said he was the vine, afterall. And that lack of faith separated them from the Church, here represented by the Apostles, whose faith in Jesus. allowed them to stay even when they didn’t understand everything.