polygraph

noun

poly·​graph ˈpä-lē-ˌgraf 

: an instrument for recording variations of several different pulsations (as of physiological variables) simultaneously compare lie detector

polygraphic

ˌpä-lē-ˈgra-fik 

adjective

Did you know?

With its graph- root, polygraph indicates that it writes out several different results. A polygraph's output consists of a set of squiggly lines on a computer screen, each indicating one function being tested. The functions most commonly measured are blood pressure, breathing rate, pulse, and perspiration, all of which tend to increase when you lie. Polygraphs have been in use since 1924, and have gotten more sensitive over the years, though many experts still believe that they're unreliable and that a prepared liar can fool the machine. They're used not only for law enforcement but perhaps more often by employers--often the police department itself!--who don't want to hire someone who has broken the law in the past but won't admit to it.

Synonyms

• lie detector

Examples of polygraph in a Sentence

They hooked him up to the polygraph and began the test.

She was asked to take a polygraph.

Recent Examples on the Web

Following his arrest in 1957, Gein was suspected of Hartley's abduction, a case which had gone cold, but he was cleared by police after passing a polygraph test, per The Victoria Advocate. —Randall Colburn, Entertainment Weekly, 15 Oct. 2025

Police officers, including Heskett, are hired after multiple interviews, an integrity test, ride-along evaluations, a polygraph, a psychological evaluation, drug screenings, medical screenings and extensive background checks, city of Lafayette spokesperson Natalie Miller said in a statement. —Lauren Penington, Denver Post, 22 Sep. 2025

Patel fielded a number of questions about polygraph tests that have been given to agents, as well as other questions asked seeking the political persuasion of agents. —Rebecca Beitsch, The Hill, 16 Sep. 2025

Katie meets with Jenn, her last hope for a friend on the show, with a manila envelope inside of which she’s printed out several pages from a website that employs Wendie, the polygraph tech with a Bettie Page haircut. —Peter Larsen, Oc Register, 5 Sep. 2025

Word History

Etymology

borrowed from French polygraphe, from poly- poly- + -graphe -graph

Note: As a word for such an instrument, polygraphe was apparently introduced by the French physiologist and inventor Étienne-Jules Maret (1830-1904). Compare "Des appareils enregistreurs en biologie," part 6 of "Histoire naturelle des corps organisés," Revue des cours scientifiques de la France et de l'étranger, 4. annéee (1867), p. 695: "Je vais mettre sous vos yeux l'enregistreur perfectionné que j'emploie aujourd'hui dans un grand nombre de circonstances. J'appelle polygraphe cet appareil, qui peut fournir le graphique d'un grand nombre de phénomènes différents." ("I am going to place before your eyes a perfected recording device that I have used in a great number of situations. I am calling this device a polygraph, which can provide a graphic record of a great number of different phenomena.") The word polygraph had been used earlier in English for a voluminous or versatile writer (after Greek polýgraphos "writing much"), an imitator, and an instrument resembling a pantograph.

First Known Use

1871, in the meaning defined above

Rhymes for polygraph

• autograph
• biograph
• cenotaph
• chronograph
• epigraph
• epitaph
• hodograph
• holograph
• hydrograph
• lithograph
• micrograph
• monograph

Kids Definition

polygraph

noun

poly·​graph ˈpäl-i-ˌgraf 

: an instrument for recording changes in several bodily functions (as blood pressure and rate of breathing) at the same time

compare lie detector

Medical Definition

polygraph

noun

poly·​graph ˈpäl-i-ˌgraf 

: an instrument for simultaneously recording variations of several different pulsations (as of the pulse, blood pressure, and respiration) see lie detector

polygraphic

ˌpäl-i-ˈgraf-ik 

adjective

polygraphically

-i-k(ə-)lē 

adverb

Legal Definition

polygraph

noun

poly·​graph ˈpä-lē-ˌgraf 

: an instrument that records physiological pulsations

especially : lie detector

polygraphic

ˌpä-lē-ˈgra-fik 

adjective