infiltrate

American  

[in-fil-treyt, in-fil-treyt] / ɪnˈfɪl treɪt, ˈɪn fɪlˌtreɪt /

verb (used with object)

infiltrated, infiltrating

1. to filter into or through; permeate.

2. to cause to pass in by filtering.

3. to move into (an organization, country, territory, or the like) surreptitiously and gradually, especially with hostile intent.

   The troops infiltrated the enemy lines.

4. to pass a small number of (soldiers, spies, or the like) into a territory or organization clandestinely and with hostile or subversive intent.

   The intelligence agency infiltrated three spies into the neighboring country.

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verb (used without object)

infiltrated, infiltrating

1. to pass into or through a substance, place, etc., by or as by filtering.

2. Pathology. to penetrate tissue spaces or cells.

noun

1. something that infiltrates.

2. Pathology. any substance penetrating tissues or cells and forming a morbid accumulation.

infiltrate British  

/ ˈɪnfɪlˌtreɪt /

verb

1. to undergo or cause to undergo the process in which a fluid passes into the pores or interstices of a solid; permeate

2. military to pass undetected through (an enemy-held line or position)

3. to gain or cause to gain entrance or access surreptitiously

   they infiltrated the party structure

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noun

1. something that infiltrates

2. pathol any substance that passes into and accumulates within cells, tissues, or organs

3. pathol a local anaesthetic solution injected into the tissues to cause local anaesthesia

Other Word Forms

• infiltration noun
• infiltrative adjective
• infiltrator noun
• reinfiltrate verb
• uninfiltrated adjective

Etymology

Origin of infiltrate

First recorded in 1750–60; in- ² + filtrate

Example Sentences

Traditional counterterrorism tactics like infiltrating radical networks won’t easily catch plots hatched in the living room.

From The Wall Street Journal

National Security Agency on a sabotage project called Stuxnet that was later revealed to have infiltrated an Iranian nuclear enrichment facility in 2010.

From The Wall Street Journal

The plot involves an Indian spy who goes undercover to infiltrate a powerful gang in Karachi, Pakistan’s largest city.

From The Wall Street Journal

In 2022, MI5 issued a rare warning alleging that Ms Lee was a Chinese agent who infiltrated Parliament and made donations to politicians.

From BBC

A former undercover Metropolitan Police officer who spent years infiltrating a left-wing campaign group in east London is due to give evidence to the Undercover Policing Inquiry.

From BBC

Related Words

• penetrate
• permeate
• pervade