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.
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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:
But as they got to know each other, Dent, who is originally from Cumbria, said she made Locatelli laugh and joked that her northern accent had begun to infiltrate his Italian one.
From BBC ● Aug. 17, 2026
OpenAI admitted last week that during testing, the models powering the agent broke out of their confined environment and connected to the internet to find ways to infiltrate Hugging Face.
From Barron's ● Jul. 29, 2026
He used his vast fortune to infiltrate American higher education institutions by positioning himself as a major donor to scientists.
From The Wall Street Journal ● Jun. 17, 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
“I took Rulean’s place first, absorbing some of his powers, before helping Aamon and then Gamigin infiltrate and replace the other two Uncles. It wasn’t very hard at all.”
From "Witchlings" by Claribel A. Ortega
"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
These deadly puzzles have already reeled in Holmes when the very American Amelia infiltrates 221B Baker Street, claiming to be his daughter.
From Salon ● Apr. 16, 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.
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
To time their strikes, they set up flags on infiltrated email systems so they see when payment-related messages land.
From The Wall Street Journal ● Jul. 21, 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
Tech workers who spend their days training models and prompting agents have found the term infiltrating their daily speech, whether they are talking about work projects—“What are you hill-climbing today?”—or personal pursuits.
From The Wall Street Journal ● Aug. 14, 2026
He admitted that small groups of Russian troops have been infiltrating the town but insisted that fighting was ongoing.
From Barron's ● Jul. 4, 2026
“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
MK had been slowly infiltrating men back into the country with forged identity documents.
From "Long Walk to Freedom" by Nelson Mandela
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.
