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
In 2015, the FBI warned him that a Chinese spy had tried to infiltrate his office by fundraising on his behalf.
—
William Melhado, Sacbee.com, 13 Apr. 2026
It's been four years since Christine Marie and Tolga Katas infiltrated Samuel Bateman's polygamist sect while working on a documentary — a daring move that would eventually lead to his conviction.
—Emily Blackwood, PEOPLE, 11 Apr. 2026
Swalwell cut off ties with Christine Fang, or Fang Fang, in 2015 after intelligence officials warned him and other members of Congress about Chinese efforts to infiltrate legislators’ offices.
—Seema Mehta, Los Angeles Times, 10 Apr. 2026
Though fur is very good at creating a warm, protective layer against wind, water is very good at infiltrating small spaces.
—Encyclopedia Britannica, 8 Apr. 2026
See All Example Sentences for infiltrate
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William Melhado, Sacbee.com, 13 Apr. 2026
It's been four years since Christine Marie and Tolga Katas infiltrated Samuel Bateman's polygamist sect while working on a documentary — a daring move that would eventually lead to his conviction.
—Emily Blackwood, PEOPLE, 11 Apr. 2026
Swalwell cut off ties with Christine Fang, or Fang Fang, in 2015 after intelligence officials warned him and other members of Congress about Chinese efforts to infiltrate legislators’ offices.
—Seema Mehta, Los Angeles Times, 10 Apr. 2026
Though fur is very good at creating a warm, protective layer against wind, water is very good at infiltrating small spaces.
—Encyclopedia Britannica, 8 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 16 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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