infiltration

American  

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

noun

1. the act or process of infiltrating.

2. the state of being infiltrated.

3. something that infiltrates; an infiltrate.

4. 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.

5. Geology. the seepage of water into soil or rock.

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Other Word Forms

• reinfiltration noun

Etymology

Origin of infiltration

First recorded in 1790–1800; infiltrate + -ion

Example Sentences

"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

One tactic was by far the most effective: infiltration.

From Salon • Feb. 15, 2026

California banned phones in public school classrooms beginning in January, largely in response to the infiltration of social media.

From Los Angeles Times • Feb. 9, 2026

"The primary failure identified was the refusal to provide complete and verifiable information regarding their employees, a critical requirement designed to prevent the infiltration of terrorist operatives into humanitarian structures," the ministry said.

From Barron's • Jan. 1, 2026

It is an infiltration of intellects, an inflammation.

From "The Lives of a Cell" by Lewis Thomas

Related Words

• aggression
• assault
• breach
• incursion
• infringement
• intrusion
• offensive
• onslaught
• raid
• violation