infiltrate

verb

in·​fil·​trate ˈin-(ˌ)fil-ˌtrāt How to pronounce infiltrate (audio) in-ˈfil- How to pronounce infiltrate (audio)
infiltrated; infiltrating
Synonyms of infiltratenext

transitive verb

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

intransitive verb

: to enter, permeate, or pass through a substance or area by filtering or by insinuating gradually
infiltrate noun
infiltration
ˌin-(ˌ)fil-ˈtrā-shən How to pronounce infiltrate (audio)
noun
infiltrative
ˈin-(ˌ)fil-ˌtrā-tiv How to pronounce infiltrate (audio)
in-ˈfil-trə-
adjective
infiltrator
ˈin-(ˌ)fil-ˌtrā-tər How to pronounce infiltrate (audio) in-ˈfil- How to pronounce infiltrate (audio)
noun

Synonyms

See All Synonyms & Antonyms in Thesaurus

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
Examples are automatically compiled from online sources to show current usage. Read More Opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback.
The past few weeks have felt like a Cold War thriller in which an enemy agent somehow infiltrates the top of the United States government. — David Frum, The Atlantic, 12 Mar. 2025 The ending, though, doesn't see Kimmie crippling the Bellaire dynasty so much as infiltrating it. — Randall Colburn, EW.com, 11 Mar. 2025 If ransomware infiltrates a segment containing noncritical systems, the damage remains localized. — Sameer Malhotra, Forbes, 10 Mar. 2025 Italian food products and cuisine have infiltrated just about every corner of the globe, but there’s no comparison to trying classic Italian recipes at their source—and there’s so much more than pizza, pasta, and gelato. — Laura Itzkowitz, Travel + Leisure, 9 Mar. 2025 See All Example Sentences for infiltrate

Word History

First Known Use

1758, in the meaning defined at transitive sense 4

Time Traveler
The first known use of infiltrate was in 1758

Rhymes for infiltrate

See All Rhymes for infiltrate

Browse Nearby Words

infiltrate
See all Nearby Words

Cite this Entry

“Infiltrate.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/infiltrate. Accessed 21 Mar. 2025.

Copy Citation

Share

Kids Definition

infiltrate

verb
in·​fil·​trate in-ˈfil-ˌtrāt How to pronounce infiltrate (audio) ˈin-(ˌ)fil- How to pronounce infiltrate (audio)
infiltrated; infiltrating
1
: to pass into or through by filtering
2
: to enter or become established gradually or secretly
infiltration
ˌin-(ˌ)fil-ˈtrā-shən How to pronounce infiltrate (audio)
noun
infiltrator
in-ˈfil-ˌtrāt-ər How to pronounce infiltrate (audio) ˈin-(ˌ)fil- How to pronounce infiltrate (audio)
noun

Medical Definition

infiltrate

1 of 2 verb
in·​fil·​trate in-ˈfil-ˌtrāt How to pronounce infiltrate (audio) ˈin-(ˌ) How to pronounce infiltrate (audio)
infiltrated; infiltrating

transitive verb

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

intransitive verb

: 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

More from Merriam-Webster on infiltrate

Nglish: Translation of infiltrate for Spanish Speakers

Last Updated: - Updated example sentences
Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!

Popular in Grammar & Usage

See More

The Difference Between 'i.e.' and 'e.g.'

How to Use Em Dashes (—), En Dashes (–) , and Hyphens (-)

Why is '-ed' sometimes pronounced at the end of a word?

What's the difference between 'fascism' and 'socialism'?

More Commonly Misspelled Words
See More

Popular in Wordplay

See More

What do SCOTUS, POTUS, and FLOTUS mean?

Flower Etymologies For Your Spring Garden

More Words with Remarkable Origins

Terroir, Oenophile, & Magnum: Ten Words About Wine

8 Words for Lesser-Known Musical Instruments
See More

Popular Features

See More

The Difference Between 'i.e.' and 'e.g.'

What do SCOTUS, POTUS, and FLOTUS mean?

Flower Etymologies For Your Spring Garden
See More

Games & Quizzes

See All
Play Quordle: Guess all four words in a limited number of tries. Each of your guesses must be a real 5-letter word.
Quordle Can you solve 4 words at once?
Play Blossom: Solve today's spelling word game by finding as many words as you can using just 7 letters. Longer words score more points.
Blossom Word Game Pick the best words!
Play Missing Letter: a crossword with a twist. Each of the 25 puzzle words start with a different letter of the alphabet. Which letter is missing?
Missing Letter A daily crossword with a twist
dog-in-disguise
Rhyme Disguise Quiz Pair up words that look different but sound alike.
See All