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
Still, even there, in the reddest part of red America, the girlboss has infiltrated.
—
Emma Green, New Yorker, 6 Apr. 2026
After Warren Jeffs’ arrest, what are the confluence of events that allow for a predator like Sam Bateman to infiltrate this vulnerable community?
—Savannah Walsh, Vanity Fair, 6 Apr. 2026
On the Palmyra Atoll in the central Pacific, trees and their fungal partners infiltrate coral rubble and compete with invasive coconut palms.
—Quanta Magazine, 6 Apr. 2026
In at least some of the recent cases, this involved infiltrating the victim’ delivery apps like DoorDash or Uber Eats with malware, allowing thieves to learn the victim’s address and other key information.
—Megan Cassidy, San Francisco Chronicle, 3 Apr. 2026
See All Example Sentences for infiltrate
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Emma Green, New Yorker, 6 Apr. 2026
After Warren Jeffs’ arrest, what are the confluence of events that allow for a predator like Sam Bateman to infiltrate this vulnerable community?
—Savannah Walsh, Vanity Fair, 6 Apr. 2026
On the Palmyra Atoll in the central Pacific, trees and their fungal partners infiltrate coral rubble and compete with invasive coconut palms.
—Quanta Magazine, 6 Apr. 2026
In at least some of the recent cases, this involved infiltrating the victim’ delivery apps like DoorDash or Uber Eats with malware, allowing thieves to learn the victim’s address and other key information.
—Megan Cassidy, San Francisco Chronicle, 3 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 8 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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