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

Definition of infiltrate

transitive verb

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

intransitive verb

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

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Other Words from infiltrate

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

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.
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Recent Examples on the Web Catra and the Horde have sort of stepped up their game in a lot of ways and are finding new ways to infiltrate and break down the defenses of the Rebellion. Patrick Gomez,, "She-ra showrunner Noelle Stevenson breaks down the epic season 4 trailer," 24 Oct. 2019 An indictment said Woodson and an unnamed co-conspirator would infiltrate the Snapchat accounts of their minor victims, and lock them out of the app by changing their passwords. Mario Ariza,, "Snapchat sextortionist, 29, guilty of preying on minors," 2 Oct. 2019 Baltimore’s government was struck in May by hackers who sought tens of thousands of dollars from the city after infiltrating computer systems and shutting down a majority of city servers. Luke Broadwater,, "Baltimore IT department uses ‘mind-boggling,' outdated data storage method, audit finds," 27 Sep. 2019 Their plan is to infiltrate the island and destroy the weaponry that threatens their peaceful existence. Guy Hanford, Ramona Sentinel, "‘Downton Abbey’ opens in theaters on Friday," 20 Sep. 2019 Reportedly, a central theme of the series to be shown to Russian viewers is that American operatives infiltrated the nuclear facility and orchestrated the disaster. Eric Berger, Ars Technica, "Are Russian space satellites failing? It’s now harder to find out," 18 June 2019 Judging by the screenshots included alongside the depositions, Twitch security teams appear to have infiltrated the channels and recorded much of the activity. Russell Brandom, The Verge, "Twitch is closing in on its Christchurch trolls," 29 June 2019 Baba Amr would be the last time that the foreign press was able to infiltrate a siege and refute the regime’s propaganda claims. Muhammad Idrees Ahmad, The New York Review of Books, "How Assad Made Truth a Casualty of War," 7 Sep. 2018 Ebola infiltrates its victims’ cells using spiky proteins on the virus’s outer shell, so researchers screened the antibodies for the ones that did the best job of binding to those proteins. Megan Molteni, WIRED, "Ebola Is Now Curable. Here’s How the New Treatments Work," 12 Aug. 2019

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.

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First Known Use of infiltrate

1758, in the meaning defined at transitive sense 1

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Time Traveler for infiltrate

Time Traveler

The first known use of infiltrate was in 1758

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Statistics for infiltrate

Last Updated

12 Nov 2019

Cite this Entry

“Infiltrate.” The Dictionary, Merriam-Webster Inc., Accessed 22 November 2019.

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More Definitions for infiltrate


How to pronounce infiltrate (audio) How to pronounce infiltrate (audio)

English Language Learners Definition of infiltrate

: to secretly enter or join (something, such as a group or an organization) in order to get information or do harm
: to cause (someone) to secretly enter or join a group, organization, etc.
technical : to pass into or through (something)


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

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Comments on infiltrate

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not agreeing with established beliefs

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