Definition of "extrusive" [ex•tru•sive]

• Tending to push or thrust out. (adjective)
• Tending to protrude or project. (adjective)
• Derived from magma poured out or ejected at the earth's surface. Used of igneous rocks. (adjective)

American Heritage(R) Dictionary of the English Language, Fifth Edition. Copyright (c) 2011 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.

• "If the crystallization process occurs at the Earth's surface, the rocks created are called extrusive igneous rocks."
• "Geologically, the Plateau is composed of Quaternary extrusive rocks, mostly rhyolite, basalt, and tuff."
• "Its mix of granitic, sedimentary, metamorphic, and extrusive rocks contrasts with the predominantly volcanic rocks of the Cascades (4)."