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
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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:
If SpaceX is allowed to try really hard to infiltrate your sensible money-market index fund, why not put it into something you’re actually passionate about, like an ultra-rare mint condition Umbreon card?
From Slate ● Aug. 31, 2026
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
We’ve previously reported on North Korea’s efforts to infiltrate the U.S. job market, and the data gave us a remarkable new window into their tactics.
From The Wall Street Journal ● Aug. 14, 2026
"There was no one who moved without security knowing it, and that allowed us to infiltrate counter-revolutionary organizations," he said in 2018 in a rare interview with Cuban state TV.
From Barron's ● Jun. 23, 2026
Hiding their guns, the soldiers can easily infiltrate the refugee camp and spy on our activities.
From "First They Killed My Father: A Daughter of Cambodia Remembers" by Loung Ung
The Interior Ministry, with an estimated 140,000 state security officials and 500,000 informants, monitors and infiltrates dissident movements.
From The Wall Street Journal ● Jul. 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
“Andor’s” final episodes sees Kleya utilize the skills she’d honed as Luthen’s closest and most trusted associate as she infiltrates a heavily guarded hospital to reach him.
From Los Angeles Times ● May 13, 2025
In these instances the pus shows a marked tendency to spread, strips the periosteum from the bone, perforates the outer layer of the membrane, and finally infiltrates the surrounding tissues.
From Diseases of the Horse's Foot by Harry Caulton Reeks
On Wednesday, Australian Prime Minister Anthony Albanese said that an OpenAI agent infiltrated a government-services website this summer.
From The Wall Street Journal ● Sep. 26, 2026
In the process it "infiltrated" a private statistics portal containing "non-sensitive" data from Australia's universal healthcare scheme Medicare, Prime Minister Anthony Albanese said.
From BBC ● Sep. 24, 2026
The warnings came after OpenAI disclosed that models had broken out of their test environment during evaluation, connected to the internet and infiltrated Hugging Face, a site where developers store and share code.
From Barron's ● Sep. 14, 2026
In laboratory experiments, the modified cells successfully infiltrated tumor organoids grown in dishes.
From Science Daily ● Aug. 25, 2026
Hence one has to suspect that the charcoal samples dated from the oldest human occupation levels consist of post-Clovis charcoal infiltrated with older carbon.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
Its officers, who wear civilian clothes, have a network of undercover agents and informants dedicated to monitoring and infiltrating dissident movements and independent groups such as art collectives.
From The Wall Street Journal ● Jul. 5, 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
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.
