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
Because the surface of the cornea contains multiple tiny microabrasions from your contact rubbing against it, these can function as openings for the amoeba to infiltrate—and the longer you’re exposed to it, the further in it can burrow.
—
Holly Burns, Time, 23 Oct. 2025
The Savant stars Chastain as an undercover investigator who infiltrates online hate groups and takes them down from the inside.
—Tony Maglio, HollywoodReporter, 23 Oct. 2025
Even with fewer boaters on the water, the threat of aquatic nuisance species infiltrating your favorite lake remains.
—Arkansas Online, 21 Oct. 2025
Indeed, a 2020 study found that meltwater trickling into Antarctica’s ice shelves could infiltrate cracks and force them open, a precursor to marine ice cliff instability that DeConto and colleagues envisioned.
—Evan Howell, Quanta Magazine, 20 Oct. 2025
See All Example Sentences for infiltrate
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Holly Burns, Time, 23 Oct. 2025
The Savant stars Chastain as an undercover investigator who infiltrates online hate groups and takes them down from the inside.
—Tony Maglio, HollywoodReporter, 23 Oct. 2025
Even with fewer boaters on the water, the threat of aquatic nuisance species infiltrating your favorite lake remains.
—Arkansas Online, 21 Oct. 2025
Indeed, a 2020 study found that meltwater trickling into Antarctica’s ice shelves could infiltrate cracks and force them open, a precursor to marine ice cliff instability that DeConto and colleagues envisioned.
—Evan Howell, Quanta Magazine, 20 Oct. 2025
See All Example Sentences for infiltrate
Cite this Entry
“Infiltrate.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/infiltrate. Accessed 26 Oct. 2025.
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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