Definitions for xenolithˈzɛn l ɪθ, ˈzin-
Random House Webster's College Dictionary
xen•o•lithˈzɛn l ɪθ, ˈzin-(n.)
a rock fragment foreign to the igneous rock in which it is embedded.
Origin of xenolith:
(geology) a piece of rock of different origin from the igneous rock in which it is embedded
any piece of rock having a different origin to that of the igneous rock in which it is found