Definitions for "Metamorphic rocks"
"Metamorphic" means "changed form," and this broad category of rocks indicates that the minerals and chemicals present have been significantly rearranged, usually through the action of intense heat and/or pressure. The original rocks might have been sedimentary or igneous, or even older metamorphic rocks.
Rocks of the Earth's crust which have been altered by the effects of heat, pressure or chemically active fluids.
Rocks that have been transformed in response to profound changes of temperature, pressure, and chemical environment without ever melting.