intrusion

noun

in·​tru·​sion in-ˈtrü-zhən 

1

: the act of intruding or the state of being intruded

especially : the act of wrongfully entering upon, seizing, or taking possession of the property of another

2

: the forcible entry of molten rock or magma into or between other rock formations

also : the intruded magma

Examples of intrusion in a Sentence

Recent Examples on the Web

Limiting runoff from pesticides and fertilizers often used on lawns can reduce saltwater intrusion in aquifers and contamination in waterways, Davidson said. —Eduardo Cuevas, USA Today, 4 Sep. 2025

Ross, 52, was not home at the time of the intrusion. —Madison E. Goldberg, People.com, 3 Sep. 2025

Many enterprises now mandate 2FA for key systems, which protects against more than 99% of intrusions. —Zak Doffman, Forbes.com, 31 Aug. 2025

Researchers say these intrusions align with activity from the extortion group ShinyHunters, with some overlap in tactics and infrastructure linked to other threat actors like Scattered Spider. —Kurt Knutsson, FOXNews.com, 31 Aug. 2025

Word History

Etymology

Middle English, from Anglo-French, from Medieval Latin intrusion-, intrusio, from Latin intrudere

First Known Use

15th century, in the meaning defined at sense 1

Phrases Containing intrusion

• anti-intrusion

Rhymes for intrusion

• allusion
• collusion
• conclusion
• confusion
• contusion
• delusion
• diffusion
• effusion
• exclusion
• extrusion
• illusion
• inclusion

Kids Definition

intrusion

noun

in·​tru·​sion in-ˈtrü-zhən 

1

: the act of intruding : the state of being intruded

2

: the entry by force of melted rock into or between other rock formations

Legal Definition

intrusion

noun

in·​tru·​sion in-ˈtrü-zhən 

1

a

: the entry at common law of a stranger after a particular estate of freehold is determined before the person who holds it in remainder or reversion has taken possession

b

: the act of wrongfully entering upon, seizing, or taking possession of the property of another

2

: a trespassing on or encroachment upon something (as a right)

the Fourth Amendment demands that the showing of justification match the degree of intrusion

—Berger v. New York, 388 U.S. 41 (1968)