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
At Saturday night’s dinner, people infiltrated the hotel to protest the Iran war and Defense Secretary Pete Hegseth.
—
Ana Ceballos
follow, Los Angeles Times, 26 Apr. 2026
In 2013, according to the Department of Justice, a hacker affiliated with the Islamic Revolutionary Guard Corps infiltrated the control system of a dam in New York State.
—Sue Halpern, New Yorker, 24 Apr. 2026
The 11-count indictment alleges that the civil rights nonprofit organization, best known for its work to oppose the Ku Klux Klan, lied to donors about paying confidential informants to infiltrate hate groups and deceived banks about the bank accounts used to make those payments.
—Sarah N. Lynch, CBS News, 23 Apr. 2026
The indictment came shortly after SPLC revealed the existence of a criminal investigation into its program to pay informants to infiltrate extremist groups and gather information on their activities.
—Collin Binkley, Chicago Tribune, 21 Apr. 2026
See All Example Sentences for infiltrate
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Ana Ceballos
follow, Los Angeles Times, 26 Apr. 2026
In 2013, according to the Department of Justice, a hacker affiliated with the Islamic Revolutionary Guard Corps infiltrated the control system of a dam in New York State.
—Sue Halpern, New Yorker, 24 Apr. 2026
The 11-count indictment alleges that the civil rights nonprofit organization, best known for its work to oppose the Ku Klux Klan, lied to donors about paying confidential informants to infiltrate hate groups and deceived banks about the bank accounts used to make those payments.
—Sarah N. Lynch, CBS News, 23 Apr. 2026
The indictment came shortly after SPLC revealed the existence of a criminal investigation into its program to pay informants to infiltrate extremist groups and gather information on their activities.
—Collin Binkley, Chicago Tribune, 21 Apr. 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 27 Apr. 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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