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

With its mission for safe AI and its unorthodox corporate structure, Anthropic’s Wall Street debut can be viewed as a guinea pig for AI frontier labs and how they are received by investors. — John Towfighi, CNN Money, 3 Nov. 2026

Mando is a guinea pig who wants to enjoy quiet time and hang out on your lap, according to Our Companions Animal Rescue. — Our Companions, Hartford Courant, 2 Nov. 2026

Readers share personal experiences with guinea pigs and other therapy animals, emphasizing their therapeutic benefits and the responsibilities of pet ownership. — Andrea Sachs, Washington Post, 30 Oct. 2026

Near the floating wooden patio, roughly 30 feet away, is a calico guinea pig eating a pile of spaghetti. — Nina Corcoran, Pitchfork, 21 Oct. 2026

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