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

Rabbits can transmit diseases to guinea pigs and may bully them. —Maria Azzurra Volpe, MSNBC Newsweek, 22 Aug. 2025

After 1,145 adoptions already this month, there are currently 854 adoptable animals — 369 dogs, 19 puppies, 165 cats, 106 kittens, 89 guinea pigs and 54 reptiles — in the organization’s care. —Caleb Lunetta, San Diego Union-Tribune, 21 Aug. 2025

At the moment that involves using her friends as guinea pigs, a job her fans would no doubt love to sign up for. —Kansas City Star, 14 Aug. 2025

Everyone is a guinea pig in an unguided and wanton impactful experiment. —Lance Eliot, Forbes.com, 8 Aug. 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