infiltrate
Americanverb (used with object)
-
infiltrates,
present (3rd person singular)
-
infiltrated,
past participle, past
-
infiltrating
present participle
-
to filter into or through; permeate.
-
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.
-
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)
-
infiltrates,
present (3rd person singular)
-
infiltrated,
past participle, past
-
infiltrating
present participle
-
to pass into or through a substance, place, etc., by or as by filtering.
-
Pathology. to penetrate tissue spaces or cells.
noun
-
something that infiltrates.
-
Pathology. any substance penetrating tissues or cells and forming a morbid accumulation.
verb
-
to undergo or cause to undergo the process in which a fluid passes into the pores or interstices of a solid; permeate
-
military to pass undetected through (an enemy-held line or position)
-
to gain or cause to gain entrance or access surreptitiously
they infiltrated the party structure
noun
-
something that infiltrates
-
pathol any substance that passes into and accumulates within cells, tissues, or organs
-
pathol a local anaesthetic solution injected into the tissues to cause local anaesthesia
Other Word Forms
Derived Forms
Inflected Forms
Participles
Conjugated Forms
Present
-
infiltratesimple
-
infiltratessimple
-
have infiltratedperfect
-
has infiltratedperfect
-
am infiltratingprogressive
-
are infiltratingprogressive
-
is infiltratingprogressive
-
have been infiltratingperfect progressive
-
has been infiltratingperfect progressive
Past
-
infiltratedsimple
-
had infiltratedperfect
-
was infiltratingprogressive
-
were infiltratingprogressive
-
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
Looking to grow your vocabulary? Check out this interactive, curated word list from our team of English language specialists at Vocabulary.com – one of over 17,000 lists we've built to help learners worldwide!
Vocabulary: A Rapper's Delight!
Interested in learning more words like this one? Our team at Vocabulary.com has got you covered! You can review flashcards, quiz yourself, practice spelling, and more – and it's all completely free to use!
While the World Watched
Want to remember this word for good? Start your learning journey today with our library of interactive, themed word lists built by the experts at Vocabulary.com – we'll help you make the most of your study time!
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:
The rapid growth of AI companies including OpenAI and Anthropic has created opportunities to infiltrate their workforces with insider threats.
From The Wall Street Journal ● Oct. 15, 2026
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
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," 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."
From Barron's ● Nov. 9, 2025
This realistic tone rooted in ambiguity and the destruction of New York City infiltrates "Cloverfield’s" poster.
From Salon ● Apr. 26, 2024
One of the first scenes Chao and Hong filmed together finds Jin learning about Ye’s involvement with the San-Ti at a meeting she infiltrates in Episode 4.
From Los Angeles Times ● Mar. 25, 2024
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
An OpenAI agent went "rogue" and "infiltrated" a private statistics portal containing "non-sensitive" data from Australia's universal healthcare scheme Medicare in June in what cyber-security experts said was the first hack of its kind.
From BBC ● Oct. 6, 2026
Australia in September said an OpenAI agent infiltrated a government website to gain access to both public and nonpublic files in the country’s healthcare-statistics portal.
From The Wall Street Journal ● Oct. 6, 2026
“Our fellow creatures have infiltrated the circuits of our brain and the fabric of our culture,” he writes.
From The Wall Street Journal ● Oct. 2, 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
He and President Roosevelt wanted Hitler to believe that American spies had infiltrated the German sabotage school and the German Army.
From Nazi Saboteurs by Samantha Seiple
The sudden influx of Bogong moths along Australia's east coast has caused a stir in cities like Sydney and Canberra, with people filming them infiltrating their homes and cars.
From BBC ● Oct. 1, 2026
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
For weeks they had been silently infiltrating South Vietnam, and they struck with a coordinated fury that shocked everyone.
From "Boots on the Ground: America's War in Vietnam" by Elizabeth Partridge
Random Word
Spin the wheel and learn a new word!
Get a wordDefinitions 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.
