[ in-troo-zhuhn ]
/ ɪnˈtru ʒən /
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See synonyms for: intrusion / intrusions on Thesaurus.com

an act or instance of intruding.
the state of being intruded.
  1. an illegal act of entering, seizing, or taking possession of another's property.
  2. a wrongful entry after the determination of a particular estate, made before the remainderman or reversioner has entered.
  1. emplacement of molten rock in preexisting rock.
  2. plutonic rock emplaced in this manner.
  3. a process analogous to magmatic intrusion, as the injection of a plug of salt into sedimentary rocks.
  4. the matter forced in.
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Origin of intrusion

1250–1300; Middle English <Medieval Latin intrūsiōn- (stem of intrūsiō), equivalent to Latin intrūs(us), past participle of intrūdere to intrude (equivalent to intrūd- verb stem + -tus past participle suffix, with dt<s) + -iōn--ion


in·tru·sion·al, adjective
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use intrusion in a sentence

British Dictionary definitions for intrusion

/ (ɪnˈtruːʒən) /

the act or an instance of intruding; an unwelcome visit, interjection, etcan intrusion on one's privacy
  1. the movement of magma from within the earth's crust into spaces in the overlying strata to form igneous rock
  2. any igneous rock formed in this way
property law an unlawful entry onto land by a stranger after determination of a particular estate of freehold and before the remainderman or reversioner has made entry

Derived forms of intrusion

intrusional, adjective
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

Scientific definitions for intrusion

[ ĭn-trōōzhən ]

The movement of magma through cracks in underground rocks within the Earth, usually in an upward direction.♦ Rocks that form from the underground cooling of magma are generally coarse-grained (because they cool slowly so that large crystals have time to grow) and are called intrusive rocks. Compare extrusion.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.