[ in-troo-zhuhn ]
See synonyms for: intrusionintrusions on

  1. an act or instance of intruding.

  2. the state of being intruded.

  1. Law.

    • an illegal act of entering, seizing, or taking possession of another's property.

    • a wrongful entry after the determination of a particular estate, made before the remainderman or reversioner has entered.

  2. Geology.

    • emplacement of molten rock in preexisting rock.

    • plutonic rock emplaced in this manner.

    • a process analogous to magmatic intrusion, as the injection of a plug of salt into sedimentary rocks.

    • the matter forced in.

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

Other words from intrusion

  • in·tru·sion·al, adjective Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2023

How to use intrusion in a sentence

British Dictionary definitions for intrusion


/ (ɪnˈtruːʒən) /

  1. the act or an instance of intruding; an unwelcome visit, interjection, etc: an intrusion on one's privacy

    • the movement of magma from within the earth's crust into spaces in the overlying strata to form igneous rock

    • any igneous rock formed in this way

  1. 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 ]

  1. 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.