guinea pig

American  

noun

1. 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.

2. Informal. the subject of any sort of experiment.

   I've volunteered as a guinea pig in several clinical trials.

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guinea pig British  

noun

1. a domesticated cavy, probably descended from Cavia porcellus, commonly kept as a pet and used in scientific experiments

2. a person or thing used for experimentation

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Etymology

Origin of guinea pig

First recorded in 1655–65

Example Sentences

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

At the center of the story is the cuy, a guinea pig eaten in Andean South America, though in this telling they’re also used in a version of bullfighting.

From Los Angeles Times • Aug. 16, 2025

When he first revealed his diagnosis in December, Smith said he wanted "be a guinea pig" for treatment options.

From BBC • Mar. 19, 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

Southwest, the llama / alpaca and the guinea pig in the Andes, the Muscovy duck in tropical South America, and the dog throughout the Americas.

From "Guns, Germs, and Steel: The Fates of Human Societies" by Jared M. Diamond

Related Words

• experimental subject
• subject
• test subject