infiltration

American

[in-fil-trey-shuhn] / ˌɪn fɪlˈtreɪ ʃən /

noun

the act or process of infiltrating.
the state of being infiltrated.
something that infiltrates; an infiltrate.
Military.
1. a method of attack in which small bodies of soldiers or individual soldiers penetrate the enemy's line at weak or unguarded points in order to assemble behind the enemy position and attack it from the rear, harass enemy rear-area installations, etc.
2. a system of transporting troops or vehicles at extended and irregular intervals so as to avoid enemy observation or attack, especially from the air.
Geology. the seepage of water into soil or rock.

Other Word Forms

reinfiltration noun

Etymology

Origin of infiltration

First recorded in 1790–1800; infiltrate + -ion

Example Sentences

Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.

"We show that increased infiltration of T cells that are attacking tumor cells translates into a therapeutic benefit for patients with glioblastoma," said Chiocca, who is also a co-senior author of the study.

From Science Daily • Mar. 20, 2026

In a statement on Monday, Hezbollah said it detected "the infiltration of approximately 15 Israeli enemy helicopters" from the Syrian side of the border in eastern Lebanon, an area where Hezbollah holds sway.

From Barron's • Mar. 8, 2026

Analysts estimate the area is smaller and that Ukraine has mainly cleared the area of Russian infiltration teams.

From The Wall Street Journal • Feb. 24, 2026

One tactic was by far the most effective: infiltration.

From Salon • Feb. 15, 2026

It is an infiltration of intellects, an inflammation.

From "The Lives of a Cell" by Lewis Thomas

Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023