(1):
(a.) Pertaining to, produced by, or exhibiting, certain changes which minerals or rocks may have undergone since their original deposition; - especially applied to the recrystallization which sedimentary rocks have undergone through the influence of heat and pressure, after which they are called metamorphic rocks.
(2):
(a.) Subject to change; changeable; variable.
(3):
(a.) Causing a change of structure.