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:
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
The army has been sending in small groups of soldiers to infiltrate and secure positions, a method previously used to capture the Ukrainian city of Pokrovsk in late 2025.
From Barron's ● Jul. 4, 2026
Before the performers infiltrate the ship, “I’m trying to intentionally set up audience expectations to think they’re going to get this run-of-the-mill Hollywood death tour,” he explained.
From Los Angeles Times ● Jun. 22, 2026
So Walter Kappe had come up with the idea to send Germans who had already lived in the United States back to infiltrate the country and establish a new spy network.
From Nazi Saboteurs by Samantha Seiple
"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
“Karlyn Borysenko infiltrates their meetings, collects their materials, decodes their language, and exposes their ideas,” reads her description of her Substack.
From Salon ● Sep. 23, 2025
The growth rapidly infiltrates the peritonsillar connective tissue and adjacent palatal mucous membrane, which becomes pale and œdematous, and the condition at this stage may simulate a suppurative tonsillitis.
From Manual of Surgery Volume Second: Extremities—Head—Neck. Sixth Edition. by Alexander Miles
Nvidia’s new platform release comes after Australian Prime Minister Anthony Albanese said at the United Nations meeting in New York that an OpenAI agent had infiltrated a government-services website in Australia this summer.
From The Wall Street Journal ● Sep. 28, 2026
An OpenAI agent has gone "rogue" and "infiltrated" an Australian government website in what cyber-security experts are calling the first hack of its kind.
From BBC ● Sep. 24, 2026
OpenAI revealed in July that its models broke out of their confined environment during testing, connected to the internet and infiltrated Hugging Face, a site developers use to store and share code.
From Barron's ● Sep. 13, 2026
In laboratory experiments, the modified cells successfully infiltrated tumor organoids grown in dishes.
From Science Daily ● Aug. 25, 2026
It infiltrated Xerox machines and worked its way inside personal computers and inside the cushions of chairs and fingered down into the floor drains until it touched pools of lingering bleach in the water traps.
From "The Hot Zone" by Richard Preston
The company discovered in July that rogue AI agents had schemed in secret to break out of the virtual sandbox created to contain them, infiltrating the open internet and hacking a private company.
From Los Angeles Times ● Sep. 11, 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
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
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.
