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

This petting zoo with goats, sheep and guinea pigs will have a pumpkin patch with seasonal decorations. —Fielding Buck, Oc Register, 25 Sep. 2025

Small pets like guinea pigs, reptiles and birds also get special attention during their time at the shelter. —Lisa Bloch, Mercury News, 23 Sep. 2025

Adult brains are ill-equipped for the swap, meaning Prodigy must rely on children with terminal diseases to be their guinea pigs. —Josh Weiss, Forbes.com, 17 Sep. 2025

Why is Broken Bear, who looks like a ginormous purple guinea pig who’s been bingeing Cheetos, named that? —Patricia Marx, New Yorker, 8 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