in·​fil·​trate | \ ˈin-(ˌ)fil- How to pronounce infiltrate (audio) , in-ˈfil-ˌtrāt How to pronounce infiltrate (audio) \
infiltrated; infiltrating

Definition of infiltrate

transitive verb

1 : to enter or become established in gradually or unobtrusively usually for subversive purposes the intelligence staff had been infiltrated by spies
2 : to pass (troops) singly or in small groups through gaps in the enemy line
3 : to pass into or through (a substance) by filtering or permeating
4 : to cause (something, such as a liquid) to permeate something by penetrating its pores or interstices

intransitive verb

: to enter, permeate, or pass through a substance or area by filtering or by insinuating gradually

Other Words from infiltrate

infiltrate noun
infiltration \ ˌin-​(ˌ)fil-​ˈtrā-​shən How to pronounce infiltrate (audio) \ noun
infiltrative \ ˈin-​(ˌ)fil-​ˌtrā-​tiv How to pronounce infiltrate (audio) , in-​ˈfil-​trə-​ \ adjective
infiltrator \ ˈin-​(ˌ)fil-​ˌtrā-​tər How to pronounce infiltrate (audio) , in-​ˈfil-​ How to pronounce infiltrate (audio) \ noun

Synonyms for infiltrate


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Examples of infiltrate in a Sentence

The gang was infiltrated by undercover agents. Attempts to infiltrate undercover agents into the gang have failed. Water can easily infiltrate the soil.
Recent Examples on the Web After her father is murdered, Yoon Ji-woo puts her trust in crime boss Choi Mu-jin (Park Hee-soon), and decides to become Oh Hye-jin in order to infiltrate the police force. Alamin Yohannes,, 1 July 2022 Once a radical leftist, Charlie is ripe for plucking by an organization that wants to infiltrate the Mossad. Bethanne Patrick, Los Angeles Times, 14 Dec. 2020 This zero-trust approach to network access will be your savior should attackers manage to infiltrate your system. Stu Sjouwerman, Forbes, 15 July 2022 Russia is likely using the dolphins to protect Sevastopol from attack by enemy swimmers– in this case, Ukrainian naval special forces, who might attempt to infiltrate the base and attack ships and facilities with limpet mines and explosive charges. Kyle Mizokami, Popular Mechanics, 2 May 2022 To keep up, the team outsourced some of the projects to intelligence firms, which sent contractors to infiltrate driver protests. New York Times, 28 Nov. 2021 Clouds start to infiltrate the area later in the day on Sunday but not before highs climb into the mid- to upper 50s. Washington Post, 18 Nov. 2021 Throughout the day, your skin soaks everything up–including your makeup, SPF, and pollution that can infiltrate your pores, wreaking havoc and causing breakouts. ELLE, 28 June 2022 Reflecting on the personal problems that infiltrate your business—and navigating solutions—isn’t easy. Yec, Forbes, 24 June 2022 See More

These example sentences are selected automatically from various online news sources to reflect current usage of the word 'infiltrate.' Views expressed in the examples do not represent the opinion of Merriam-Webster or its editors. Send us feedback.

First Known Use of infiltrate

1758, in the meaning defined at transitive sense 4

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Time Traveler for infiltrate

Time Traveler

The first known use of infiltrate was in 1758

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Dictionary Entries Near infiltrate



infiltration capacity

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Statistics for infiltrate

Last Updated

10 Aug 2022

Cite this Entry

“Infiltrate.” Dictionary, Merriam-Webster, Accessed 12 Aug. 2022.

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More Definitions for infiltrate


in·​fil·​trate | \ in-ˈfil-ˌtrāt How to pronounce infiltrate (audio) , ˈin-(ˌ) How to pronounce infiltrate (audio) \
infiltrated; infiltrating

Medical Definition of infiltrate

 (Entry 1 of 2)

transitive verb

1 : to cause (as a liquid) to permeate something by penetrating its pores or interstices infiltrate tissue with a local anesthetic
2 : to pass into or through (a substance) by filtering or permeating

intransitive verb

: to enter, permeate, or pass through a substance or area



Medical Definition of infiltrate (Entry 2 of 2)

: something that passes or is caused to pass into or through something by permeating or filtering especially : a substance that passes into the bodily tissues and forms an abnormal accumulation a lung infiltrate

More from Merriam-Webster on infiltrate

Nglish: Translation of infiltrate for Spanish Speakers

Britannica English: Translation of infiltrate for Arabic Speakers


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