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.
"I wouldn't want to be the first guinea pig," as "it's not so easy to have everything just smooth" like Apple has managed to do with its laptops.
From Barron's • Jun. 1, 2026
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
That light droned down on me for years as I moved from computer games to MySpace, illuminating whatever sins I was committing as a guinea pig in the days of early social media.
From Salon • Jan. 7, 2025
Alec spent his teens and early 20s helping out around Erewhon, a fast-tracked corporate education that included partaking in the human guinea pig sample sessions led by his mother.
From Los Angeles Times • Jun. 2, 2024
The llama, guinea pig, and potato of the Andean highlands never reached the Mexican highlands, so Mesoamerica and North America remained without domestic mammals except for dogs.
From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond
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.
