Simple Definition of lie detector

from our Learner's Dictionary

lie detector

noun

plural lie detectors
: a device used to measure the heart rate, breathing, etc., in order to find out if someone (such as a person suspected of a crime) is being honest
The murder suspect failed a lie detector test.

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“Lie detector.” Merriam-Webster.com Simple Definition, Merriam-Webster, https://www.merriam-webster.com/simple/lie%20detector. Accessed 24 Jun. 2026.

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