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
Tom Hiddleston starred as a dashing military vet turned hotel night manager recruited by British intelligence to infiltrate the inner circle of Hugh Laurie’s posh, psychopathic arms dealer.
—
Judy Berman, Time, 9 Jan. 2026
Set in 1969 Palm Beach, the Apple TV series follows Kristen Wiig’s Maxine Dellacorte-Simmons, a spry social climber eager to infiltrate high society.
—Savannah Walsh, Vanity Fair, 7 Jan. 2026
On her show the evening of January 6, the Fox News host Laura Ingraham wondered aloud whether antifa sympathizers had infiltrated the crowd.
—Jamie Thompson, The Atlantic, 6 Jan. 2026
Sculptured shoulders, exaggerated silhouettes, color blocking, chunky belts and hearty gold hardware are some of the ways the trend could infiltrate the denim category.
—Angela Velasquez, Sourcing Journal, 5 Jan. 2026
See All Example Sentences for infiltrate
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Judy Berman, Time, 9 Jan. 2026
Set in 1969 Palm Beach, the Apple TV series follows Kristen Wiig’s Maxine Dellacorte-Simmons, a spry social climber eager to infiltrate high society.
—Savannah Walsh, Vanity Fair, 7 Jan. 2026
On her show the evening of January 6, the Fox News host Laura Ingraham wondered aloud whether antifa sympathizers had infiltrated the crowd.
—Jamie Thompson, The Atlantic, 6 Jan. 2026
Sculptured shoulders, exaggerated silhouettes, color blocking, chunky belts and hearty gold hardware are some of the ways the trend could infiltrate the denim category.
—Angela Velasquez, Sourcing Journal, 5 Jan. 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 13 Jan. 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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