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
Expect launch photos, snaps of historic hardware destined for space, images of the night sky and, from time to time, photographic evidence of our entertainment editor Ian Stokes infiltrating Amazon's London office to sneak a peek at their May the 4th Star Wars offering … allegedly.
—
Anthony Wood, Space.com, 2 May 2026
In The Second Lady, when America’s beloved First Lady is abducted and replaced by a Russian double, both women must fight to survive—one navigating captivity in Siberia, the other infiltrating the White House to sabotage NATO during the G7 Summit.
—Nellie Andreeva, Deadline, 30 Apr. 2026
Legends fictionalizes the true story of British customs employees who went undercover in the '90s to infiltrate drug smuggling gangs.
—Madeleine Janz, PEOPLE, 30 Apr. 2026
For anyone whose home has been infiltrated by mice, or termites, pest control is worth the cost.
—Ana Durrani, USA Today, 28 Apr. 2026
See All Example Sentences for infiltrate
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Anthony Wood, Space.com, 2 May 2026
In The Second Lady, when America’s beloved First Lady is abducted and replaced by a Russian double, both women must fight to survive—one navigating captivity in Siberia, the other infiltrating the White House to sabotage NATO during the G7 Summit.
—Nellie Andreeva, Deadline, 30 Apr. 2026
Legends fictionalizes the true story of British customs employees who went undercover in the '90s to infiltrate drug smuggling gangs.
—Madeleine Janz, PEOPLE, 30 Apr. 2026
For anyone whose home has been infiltrated by mice, or termites, pest control is worth the cost.
—Ana Durrani, USA Today, 28 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 4 May. 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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