A membrane covering (anatomy).

Therefore I will be unto them as a lion: as a leopard by the way will I observe them: I will meet them as a bear that is bereaved of her whelps, and will rend the CAUL of their heart, and there will I devour them like a lion: the wild beast shall tear them. ( Hosea 13:7-8 )

Dictionary of Words from the King James Bible. Public Domain. Copy freely.