metamorphic rock

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun geology one of the major groups of rock that makes up the crust of the Earth; consists of pre-existing rock mass in which new minerals or textures are formed at higher temperatures and greater pressures than those present on the Earth's surface

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun rock altered by pressure and heat