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.
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Recent Examples on the Web The first colder air mass will infiltrate the East over the next couple of days and into the weekend. Judson Jones, CNN, 17 Nov. 2021 If Russian hackers were able to infiltrate critical federal government agencies through the SolarWinds attack, nothing is completely safe from cyber threats. Matt Egan, CNN, 12 May 2021 O'Neal wins Hampton's trust and is ultimately able to infiltrate the Black Panther Party. Ineye Komonibo,, 13 Jan. 2021 With these shadow markets in place, hacking skills aren’t needed to target a business or its customers: nation-states, terrorist groups and profit-seekers can infiltrate a business by simply paying someone else to do it for them. Chris Olson, Forbes, 21 Oct. 2021 Fungi infiltrate the roots of almost every plant, determining so much about its life that researchers are now asking whether plants can be considered plants without them. Zoë Schlanger, The New York Review of Books, 7 Oct. 2021 Dead birds and wildlife have been washing up on Huntington Beach in Orange County, and experts worry the spill could infiltrate wetlands and other vulnerable areas, creating an ecological disaster. Aj Willingham, CNN, 4 Oct. 2021 The oversized pockets are now ready to infiltrate just about every area of our wardrobes, from elegant day dresses to work-appropriate blazers. Vogue, 25 Aug. 2021 Belarus’s government is working hard to infiltrate these groups, both within and outside the country, often by establishing numerous fake groups to lure the activists into revealing their identities, members said. New York Times, 20 Aug. 2021

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 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

26 Nov 2021

Cite this Entry

“Infiltrate.” Dictionary, Merriam-Webster, Accessed 2 Dec. 2021.

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More Definitions for infiltrate



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.
: 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

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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