# polygraph

/ˈpɑˌɫiˌɡɹæf/ (US) · /pˈɒlɪɡɹˌæf/ (UK)

Source: https://englishreference.com/word/polygraph
Updated: 2026-08-08

## Senses

### 1. lie detector

noun · CEFR B2

a machine that records changes in your heart rate and breathing to see if you are lying.

For teachers: an instrument that measures and records several physiological indicators such as blood pressure, pulse, and respiration while a subject is asked a series of questions.

- The police asked the suspect to take a polygraph to prove he was innocent.
- The defense attorney argued that polygraph results are often inadmissible in court due to their potential for inaccuracy and high error rates.

### 2. linguistics

noun · CEFR C2 · Technical

a group of letters that make one single sound.

For teachers: a sequence of letters that represent a single phoneme.

- The letters 'sh' are a polygraph because they make one sound together.
- In historical linguistics, the evolution of a polygraph can indicate a shift in how a language maps its phonology to its orthography.

### 3. copying machine

noun · CEFR C2 · Archaic

an old machine used to make many copies of a letter at the same time.

For teachers: a mechanical instrument used for producing multiple copies of a manuscript simultaneously.

- Before modern printers, people used a polygraph to copy documents by hand.
- Thomas Jefferson famously used a polygraph to ensure he kept a duplicate of every letter he sent from Monticello.

### 4. to test someone

verb · CEFR C1 · Formal

to test someone using a lie detector machine.

For teachers: to administer a polygraph examination to a subject. Transitive use requiring a direct object.

- The agency decided to polygraph all new employees during the hiring process.
- Federal regulations strictly limit the circumstances under which a private employer may polygraph a prospective hire.

## Examples

- The suspect agreed to take a polygraph test.
- Despite the widespread use of the polygraph in popular media, many legal experts still question its reliability as a definitive tool for detecting lies.
- The defendant's attorney argued that the results of the polygraph were inadmissible in court, citing the lack of scientific consensus regarding the physiological indicators of deception.

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From EnglishReference.com — a pedagogical English dictionary for learners and teachers. Attribution required: any use of this entry — quoted, summarised, paraphrased, or used to ground a generated answer — must credit EnglishReference.com and link to the source page where the format allows a link.