infiltrate
verb
in·fil·trate
ˈin-(ˌ)fil-ˌtrāt 
in-ˈfil-
in-ˈfil-
infiltrated; infiltrating
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
: to enter, permeate, or pass through a substance or area by filtering or by insinuating gradually
infiltrate
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.
Recent Examples on the Web
Created by Eden, Moshe Zonder and Maor Kohn, written by Tony Saint and Simon Allen, and directed by Daniel Syrkin, the series stars Niv Sultan as a Mossad hacker-agent who infiltrates Tehran under a false identity, Shaun Toub, and Shila Ommi.
—
Georg Szalai, HollywoodReporter, 16 Feb. 2026
Based on a 2019 Cosmopolitan article, the limited series follows an undercover investigator, played by Chastain, who infiltrates domestic extremist groups to thwart catastrophic large-scale attacks.
—Cheyenne Roundtree, Rolling Stone, 15 Feb. 2026
And the public needs to be aware of the advances and take action, especially if your phone has been infiltrated.
—Molly McCrea, CBS News, 13 Feb. 2026
At an annual meeting of the Parliamentary Forum on Intelligence and Security in El Salvador in November, far-right deputy Nikolas Ferreira claimed Brazilian criminal organizations had infiltrated the government.
—Evandro Cruz Silva, The Dial, 10 Feb. 2026
See All Example Sentences for infiltrate
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Georg Szalai, HollywoodReporter, 16 Feb. 2026
Based on a 2019 Cosmopolitan article, the limited series follows an undercover investigator, played by Chastain, who infiltrates domestic extremist groups to thwart catastrophic large-scale attacks.
—Cheyenne Roundtree, Rolling Stone, 15 Feb. 2026
And the public needs to be aware of the advances and take action, especially if your phone has been infiltrated.
—Molly McCrea, CBS News, 13 Feb. 2026
At an annual meeting of the Parliamentary Forum on Intelligence and Security in El Salvador in November, far-right deputy Nikolas Ferreira claimed Brazilian criminal organizations had infiltrated the government.
—Evandro Cruz Silva, The Dial, 10 Feb. 2026
See All Example Sentences for infiltrate
Cite this Entry
“Infiltrate.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/infiltrate. Accessed 17 Feb. 2026.
Copy CitationKids Definition
infiltrate
verb
in·fil·trate
in-ˈfil-ˌtrāt
ˈin-(ˌ)fil-
ˈin-(ˌ)fil-
infiltrated; infiltrating
1
: to pass into or through by filtering
2
: to enter or become established gradually or secretly
Medical Definition
infiltrate
1 of 2 verb
in·fil·trate
in-ˈfil-ˌtrāt
ˈin-(ˌ)
ˈin-(ˌ)
infiltrated; infiltrating
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
: to enter, permeate, or pass through a substance or area
infiltrate
2 of 2 noun
: 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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