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
When Patriot Front members filed a lawsuit against the infiltrator accusing him of “malicious doxxing,” they relied on federal law and invasion of privacy and computer fraud statutes.
From Seattle Times ● Nov. 16, 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
Trevante Rhodes, who was super in “Moonlight,” plays the infiltrator, a man torn between his job and his race.
From Washington Times ● Feb. 23, 2021
He considered that perhaps they were just checking him out, making sure he wasn’t an FBI infiltrator, but as the weeks went by, C.P. ached with disappointment.
From "The Best of Enemies" by Osha Gray Davidson
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.
