infiltrate
Americanverb (used with object)
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infiltrates,
present (3rd person singular)
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infiltrated,
past participle, past
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infiltrating
present participle
-
to filter into or through; permeate.
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to cause to pass in by filtering.
-
to move into (an organization, country, territory, or the like) surreptitiously and gradually, especially with hostile intent.
The troops infiltrated the enemy lines.
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to pass a small number of (soldiers, spies, or the like) into a territory or organization clandestinely and with hostile or subversive intent.
The intelligence agency infiltrated three spies into the neighboring country.
verb (used without object)
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infiltrates,
present (3rd person singular)
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infiltrated,
past participle, past
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infiltrating
present participle
-
to pass into or through a substance, place, etc., by or as by filtering.
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Pathology. to penetrate tissue spaces or cells.
noun
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something that infiltrates.
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Pathology. any substance penetrating tissues or cells and forming a morbid accumulation.
verb
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to undergo or cause to undergo the process in which a fluid passes into the pores or interstices of a solid; permeate
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military to pass undetected through (an enemy-held line or position)
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to gain or cause to gain entrance or access surreptitiously
they infiltrated the party structure
noun
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something that infiltrates
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pathol any substance that passes into and accumulates within cells, tissues, or organs
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pathol a local anaesthetic solution injected into the tissues to cause local anaesthesia
Other Word Forms
Derived Forms
Inflected Forms
Participles
Conjugated Forms
Present
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infiltratesimple
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infiltratessimple
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have infiltratedperfect
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has infiltratedperfect
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am infiltratingprogressive
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are infiltratingprogressive
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is infiltratingprogressive
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have been infiltratingperfect progressive
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has been infiltratingperfect progressive
Past
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infiltratedsimple
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had infiltratedperfect
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was infiltratingprogressive
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were infiltratingprogressive
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had been infiltratingperfect progressive
Future
Etymology
Origin of infiltrate
Explanation
If you infiltrate a group or organization, you join it in order to gain information, like an employee of a donut shop that infiltrates the competition to try to learn its "secret recipe" for its delicious dough. Infiltrate is a verb that is familiar to international spies and undercover agents, who are all adept at joining a group under false pretenses, fitting in, and working their way up to the highest ranks in order to find out as much information as they can about the group. The word can be used more broadly to describe anything that stealthily becomes a part of something else, such as slang words that infiltrate our everyday speech.
Vocabulary lists containing infiltrate
A Separate Peace
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Vocabulary: A Rapper's Delight!
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While the World Watched
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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.
See Examples For:
Alternatively although less likely, high pressure may be weaker, allowing low pressure systems to more readily infiltrate from the west, bringing cooler and wetter conditions.
From BBC ● Aug. 7, 2026
"There was no one who moved without security knowing it, and that allowed us to infiltrate counter-revolutionary organizations," the famously reserved politician said in 2018 in a rare interview with Cuban state TV.
From Barron's ● Jun. 21, 2026
A new wave of settlers – pastoralist-farmers hailing ultimately from the Russian steppe – began to infiltrate the Rhine area in the form of the Corded Ware culture.
From Science Daily ● May 30, 2026
Russia relied heavily on the tactic of sending forward tiny groups of soldiers to infiltrate gaps in the front line in 2025.
From The Wall Street Journal ● May 19, 2026
“With my last battalion I used to pretend that I was an orphan and infiltrate the enemy camp. They call me High-Tech because my first commander said I am better than any high-technology spying gadget.”
From "Half of a Yellow Sun" by Chimamanda Ngozi Adichie
The stakes around AI are rising as it infiltrates every aspect of the economy.
From Los Angeles Times ● Mar. 5, 2026
"When corruption infiltrates the sport, it brings disgrace not only to the participants but damages the public trust in an institution that is vital and dear to all of us," Mr Nocella added.
From BBC ● Nov. 9, 2025
"When corruption infiltrates the sport, it brings disgrace not only to the participants but damages the public trust in an institution that is vital and dear to all of us."
From Barron's ● Nov. 9, 2025
Apple also recently postponed the on-the-news thriller series called “The Savant,” starring Jessica Chastain as an undercover investigator who infiltrates online hate groups, following the killing of Charlie Kirk.
From The Wall Street Journal ● Oct. 6, 2025
And the essence infiltrates and poisons the whole atmosphere in which the would-be-free think and act.
From The Glands Regulating Personality by Louis Berman M.D.
We then take a look at a new WSJ documentary that uncovers how North Koreans have infiltrated American companies.
From The Wall Street Journal ● Aug. 15, 2026
A new WSJ documentary based on leaked data, interviews and never-before-seen videos reveals how a single team of these workers infiltrated at least eight companies in just a few months.
From The Wall Street Journal ● Aug. 14, 2026
Hilton, Lohan and their ilk infiltrated these scenes as well, and to hear Willetts tell it, the music and imagery that came out of both influenced the nightlife aesthetics everywhere, especially in the U.K.
From Los Angeles Times ● Aug. 11, 2026
It admitted last week that its models broke out of their confined environment during testing, connected to the internet, and infiltrated Hugging Face, a site where developers store and share their code.
From Barron's ● Jul. 30, 2026
In about 750 a.d., about a century after Wari came to Cerro Baul, Tiwanaku groups infiltrated the region around it.
From "1491" by Charles C. Mann
“They’re infiltrating, pretending they’re parents or they know people, but I’m the mom. I know who they are.”
From Los Angeles Times ● May 14, 2026
In Jihad in America, Emerson used hidden-camera footage to try to build a case that jihadists were infiltrating Middle America.
From Slate ● Apr. 19, 2026
“This remains a real concern for oil inflation infiltrating the global economy.”
From The Wall Street Journal ● Mar. 31, 2026
Peckham-Driver, who is from Needham Market in Suffolk, was diagnosed with deep infiltrating endometriosis after she was told her pain was down to irritable bowel syndrome or anxiety.
From BBC ● Mar. 23, 2026
Wolf specialized in infiltrating the West German government, sometimes with "Romeo spies," who would strike up romances with unsuspecting single women—many of them secretaries to powerful generals and political figures.
From "Spies: The Secret Showdown Between America and Russia" by Marc Favreau
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
