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

Over the last two seasons of Percy Jackson and the Olympians, the titular demigod (Walker Scobell) has faced off against a minotaur, sailed to the sea of monsters, been chased by Cerberus, and even magically transformed into a guinea pig. — Emlyn Travis, Entertainment Weekly, 21 July 2026

Around the corner, a self-driving truck is a guinea pig for autonomous driving software destined for Japanese roads. — Reed Albergotti, semafor.com, 21 July 2026

Other competitions will showcase small animals such as guinea pigs, rabbits, and poultry; and junior livestock including swine, dairy cattle, and beef cattle. — Sacbee.com, 16 July 2026

An animal rescue group in northwest Indiana is helping care for dozens of guinea pigs, many of which are pregnant, after they were rescued from what police said was a squalid home on Tuesday morning. — Todd Feurer, CBS News, 17 June 2026

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. porcellus) often kept as a pet and widely used in biological research

called also cavy