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 The Cavs did many things well Friday night, looking eager to silence the whispers that have infiltrated the locker room during the weeks-long struggle. Chris Fedor, cleveland, "Cleveland Cavaliers can’t quiet the noise, lose to Orlando Magic for third time this season, 93-87," 7 Dec. 2019 The Associated Press reported earlier this month that shops in downtown Los Angeles are openly selling packaging and hardware that can be used to produce counterfeit marijuana vapes that have infiltrated the state’s cannabis marketplace. Michael R. Blood, San Diego Union-Tribune, "California to consumers: Stop vaping amid investigation," 24 Sep. 2019 Ferries Instead of Bridges LUDINGTON, Mich. — Every few days, workers in Ludington pump out lake water that has infiltrated the sewer system and spilled onto an intersection. Mitch Smith, New York Times, "Summer on the Swollen Great Lakes," 24 Aug. 2019 So behind everyone who says we’re being infiltrated by shape-shifting lizard-aliens is someone struggling with the complexity of everyday life. Joshua Pease, Popular Mechanics, "How You've Been Conditioned to Love Conspiracy Theories," 17 Dec. 2019 Several Ring users nationwide have reported that their security systems were also infiltrated by hackers who harassed them through the camera's two-way talk function. Allyson Chiu, Anchorage Daily News, "A Mississippi mother installed a Ring camera in her children’s room for peace of mind. A hacker used it to harass her 8-year-old daughter.," 12 Dec. 2019 During the private event, without mentioning Bevin by name, Beshear decried how the state's institutions had been infiltrated by hate, insults and anger in recent years. Phillip M. Bailey, The Courier-Journal, "Gov. Andy Beshear emphasizes Kentucky's return to civility in inauguration speech," 10 Dec. 2019 The violence underscores the rapidly deteriorating security situation in once peaceful Burkina Faso, which has been infiltrated by jihadists who have been active for years in neighboring Mali. Washington Post, "Ambush on mining company convoy kills 37 in Burkina Faso," 7 Nov. 2019 In all of Brazil, the reserve most thoroughly infiltrated by outsiders may be Yanomami Indigenous Territory, along the northern border with Venezuela. Scott Wallace, National Geographic, "Murder in the Amazon heightens fears for isolated tribes," 27 Sep. 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

22 Jan 2020

Cite this Entry

“Infiltrate.” The Dictionary, Merriam-Webster Inc., Accessed 23 January 2020.

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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

What made you want to look up infiltrate? Please tell us where you read or heard it (including the quote, if possible).


out of the ordinary or unreasonable

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