counterintelligence

[ koun-ter-in-tel-i-juh ns ]
/ ˌkaʊn tər ɪnˈtɛl ɪ dʒəns /

noun

the activity of an intelligence service employed in thwarting the efforts of an enemy's intelligence agents to gather information or commit sabotage.
an organization engaged in counterintelligence.

Origin of counterintelligence

First recorded in 1935–40; counter- + intelligence
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2019

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British Dictionary definitions for counterintelligence

counterintelligence

/ (ˌkaʊntərɪnˈtɛlɪdʒəns) /

noun

activities designed to frustrate enemy espionage
intelligence collected about enemy espionage
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012