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[ik-stroo-siv, -ziv] /ɪkˈstru sɪv, -zɪv/
tending to extrude.
pertaining to extrusion.
Also, effusive. Geology. noting or pertaining to a class of igneous rocks that have been forced out in a molten or plastic condition upon the surface of the earth.
Origin of extrusive
1810-20; extrus(ion) + -ive
Related forms
nonextrusive, adjective Unabridged
Based on the Random House Dictionary, © Random House, Inc. 2015.
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Examples from the web for extrusive
  • extrusive rocks are more difficult to clearly identify because the mineral grains are typically invisible.
  • Igneous rocks are divided into two groups, intrusive or extrusive, depending upon where the molten rock solidifies.
  • These rocks are characterized as either extrusive or intrusive.
  • extrusive rocks are made of small, often microscopic crystals, which indicate rapid cooling and little time for crystal growth.
  • Once you know you have an igneous rock, look at the texture to decide if it is intrusive or extrusive.
  • The rock capping the mesa is an extrusive form of granite called rhyolite.
  • Deposits related to subaerial mafic extrusive rocks.
  • The dam is located in a narrow steep-sided valley cut through several hundred of igneous extrusive and extrusive rock.
  • Show me all extrusive igneous rock units that contain sanidine.
  • Display all extrusive igneous rock units that contain sanidine.
British Dictionary definitions for extrusive


tending to extrude
(of igneous rocks) formed from magma issuing from volcanoes or cracks in the earth's crust; volcanic Compare intrusive (sense 2)
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition
© William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins
Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012
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Word Origin and History for extrusive

1816, from Latin extrusus, past participle of extrudere (see extrusion) + -ive. Related: Extrusively.

Online Etymology Dictionary, © 2010 Douglas Harper
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