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
Cuba’s government accused those suspects of trying to infiltrate the island and unleash terrorism, although the exact motive remains unclear.
—
ABC News, 2 Mar. 2026
Security footage showed that Alexander Friedmann had been infiltrating the building for months.
—David Remnick, New Yorker, 2 Mar. 2026
Israel says the new measures are necessary to ensure armed groups do not infiltrate humanitarian organizations.
—Sam Mednick, Los Angeles Times, 27 Feb. 2026
The Cuban government is still fully capable of maintaining public order and defending its coastline, as the 10 people that allegedly tried to infiltrate the island found out.
—William M. Leogrande, The Conversation, 27 Feb. 2026
See All Example Sentences for infiltrate
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ABC News, 2 Mar. 2026
Security footage showed that Alexander Friedmann had been infiltrating the building for months.
—David Remnick, New Yorker, 2 Mar. 2026
Israel says the new measures are necessary to ensure armed groups do not infiltrate humanitarian organizations.
—Sam Mednick, Los Angeles Times, 27 Feb. 2026
The Cuban government is still fully capable of maintaining public order and defending its coastline, as the 10 people that allegedly tried to infiltrate the island found out.
—William M. Leogrande, The Conversation, 27 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 5 Mar. 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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