guinea pig

noun

1

: a small stout-bodied short-eared tailless domesticated rodent (Cavia porcellus) of South American origin often kept as a pet and widely used in biological research

called also cavy

2

: a subject of research, experimentation, or testing

Examples of guinea pig in a Sentence

He volunteered to act as a guinea pig in the experiment.

Recent Examples on the Web

When kids become the 'guinea pigs' Edtech is a massive industry that's only grown since the pandemic. —Lily Altavena, Freep.com, 24 Nov. 2025

Friends Guinea Pig Playground Set With a near-perfect rating and over 8,000 recent purchases, this guinea pig playground set is a great gift for builders ages 7 and up. —Mia Huelsbeck, PEOPLE, 15 Nov. 2025

So when Gear & Affiliate Director Kristen Geil volunteered as a guinea pig before the 2025 Berlin Marathon, Outside Lab Test Editor Adam Trenkamp saw a golden opportunity to test a super shoe’s real-world performance, then compare that data with its lab performance using the Heeluxe Time Machine. —Adam Trenkamp, Outside, 4 Nov. 2025

Until the twentieth century, primates were considered too big, feral, and expensive for most experiments; researchers favored guinea pigs, frogs, rabbits, and dogs. —Ava Kofman, New Yorker, 3 Nov. 2025

Word History

First Known Use

1664, in the meaning defined at sense 1

Rhymes for guinea pig

• whirligig
• big
• brig
• brigg
• dig
• fig
• gig
• jig
• mig
• prig
• rig
• sprig

Kids Definition

guinea pig

noun

1

: a small stocky rodent with short ears and a very short tail that is often kept as a pet and is used in biological research

2

: a person or thing experimented on

Medical Definition

guinea pig

noun

guin·​ea pig ˈgin-ē-ˌ 

: a small stout-bodied short-eared nearly tailless domesticated rodent of the genus Cavia (C. porcellus) often kept as a pet and widely used in biological research

called also cavy