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

The farm is home to goats, Holstein cows, potbellied and kune kune pigs, donkeys, sheep, rabbits, llamas, alpacas, guinea fowl, guinea pigs, geese, chickens, a Shetland pony, and a Shire horse. —Rachel Raposas, PEOPLE, 23 Oct. 2025

And yes, people can show up with all sorts of pets some days, including guinea pigs, rabbits, chickens, lizards, snakes, a praying mantis, brine shrimp, rats, and ferrets. —Susan Tompor, Freep.com, 22 Oct. 2025

At the time of the theft, the sanctuary was preparing to relocate the guinea pigs to Phoenix. —Wren Smetana, AZCentral.com, 28 Sep. 2025

This petting zoo with goats, sheep and guinea pigs will have a pumpkin patch with seasonal decorations. —Fielding Buck, Oc Register, 25 Sep. 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. cobaya) often kept as a pet and widely used in biological research

called also cavy