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

Also listed on the website as available for adoption are two rabbits, six guinea pigs and eight cats. —Marcus D. Smith, Sacramento Bee, 18 Jan. 2025

More:Daddy Days: Christmas with the family 5 – Getting a guinea pig. —Caleb Harris, Austin American-Statesman, 26 Dec. 2024

While both series feature a guinea pig, the spinoff also includes a bunny and a snake instead of a turtle and a duck. —Sari Hitchins, Parents, 20 Nov. 2024

The awkwardness of semi-estrangement melts away instantly when Ingrid visits the hospital and Martha explains that she’s agreed to be a guinea pig in an experimental treatment for her Stage 3 cervical cancer. —David Rooney, The Hollywood Reporter, 2 Sep. 2024

Word History

First Known Use

1664, in the meaning defined at sense 1

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