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

Once again, guinea pig/pioneer. —Mark Gray, PEOPLE, 4 Sep. 2025

Working with Adams County Animal Control, police officers removed 31 dogs and puppies, which were mostly housed in small cages in the garage, as well as two cats and two guinea pigs. —Aldo Svaldi, Denver Post, 29 Aug. 2025

Peanut is perhaps the first nonbinary rhythmic-gymnast guinea pig in literary history. —Sloane Crosley, New Yorker, 25 Aug. 2025

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