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

Essentially, Americans were used as guinea pigs for many years. —Reader Commentary, Baltimore Sun, 18 June 2025

In this backstory, Black men served as guinea pigs until the super serum that created the white Captain America, Steve Rogers, could be perfected. —Ken Makin, The Christian Science Monitor, 14 Feb. 2025

And a guinea pig, chickens, ducks, finches, a goose, rabbits, donkeys, pigs, a cow, goats, horses… Our family consisted of a menagerie of species. —Chi Varnado, San Diego Union-Tribune, 7 May 2025

These include vegetarianism, an aversion to plastic drinking straws, and the care and feeding of guinea pigs. —Kaitlyn Schallhorn, Oc Register, 20 May 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