guinea pig
Americannoun
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a short-eared, tailless rodent of the genus Cavia, usually white, black, and tawny, commonly regarded as the domesticated form of one of the South American wild species of cavy: often used in scientific experiments or kept as a pet.
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Informal. the subject of any sort of experiment.
I've volunteered as a guinea pig in several clinical trials.
noun
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a domesticated cavy, probably descended from Cavia porcellus, commonly kept as a pet and used in scientific experiments
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a person or thing used for experimentation
Etymology
Origin of guinea pig
First recorded in 1655–65
Example Sentences
Examples are provided to illustrate real-world usage of words in context. Any opinions expressed do not reflect the views of Dictionary.com.
As he buttoned up a professional baseball uniform for the first time in his life, he understood that he was becoming the guinea pig in an experiment that has the whole industry watching.
From The Wall Street Journal • Nov. 25, 2025
After all, Vanessa’s boyfriend, played by the always absurd Jason Mantzoukas, brings his very ill guinea pig to the festivities.
From Los Angeles Times • Nov. 20, 2025
His lead, Pattinson’s Mickey Barnes, is a dopey, instantly lovable voluntary “Expendable,” jettisoned into space to be a human guinea pig who will be pivotal in colonizing a faraway planet.
From Salon • Mar. 7, 2025
One surviving patient told the BBC he was treated like a "guinea pig".
From BBC • Apr. 18, 2024
The guinea pig rested in my arms tensely.
From "Life of Pi" by Yann Martel
Definitions and idiom definitions from Dictionary.com Unabridged, based on the Random House Unabridged Dictionary, © Random House, Inc. 2023
Idioms from The American Heritage® Idioms Dictionary copyright © 2002, 2001, 1995 by Houghton Mifflin Harcourt Publishing Company. Published by Houghton Mifflin Harcourt Publishing Company.
