infiltrator
Americannoun
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a soldier, intelligence agent, or other person who moves surreptitiously and gradually into an organization, territory, community, or the like, especially with hostile intent.
Using a false name, the infiltrator participated in meetings and prep sessions with the protest group and had complete access to their documentation.
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a person or thing that causes one substance to pass into another by filtering.
The roots of wetland plants serve as massive water infiltrators, allowing more rainwater to seep into the soil and recharge underground aquifers.
Etymology
Origin of infiltrator
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
They had to go with the “selfie cruise” narrative, which meant they had to treat them with basic decency because they couldn’t pass them off as some evil infiltrator.
From Slate • Sep. 29, 2025
“I just had the worst infiltrator the org has ever seen,” Brown wrote.
From Seattle Times • Aug. 8, 2023
Ukrainian agencies, Ton-That said, have used the app to confirm the identities of people at military checkpoints and to check whether a Ukrainian is a possible Russian infiltrator or saboteur.
From Washington Post • Apr. 15, 2022
They say the guard may have been a second infiltrator trying to stoke anger and deflect blame.
From New York Times • Nov. 2, 2018
“Should I—there’s no way you could be an infiltrator, is there? Can I trust you?”
From "Among the Hidden" by Margaret Peterson Haddix
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
