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
Example Sentences
He volunteered to act as a guinea pig in the experiment.
Recent Examples on the Web Especially since Altuzarra and Saks Fifth Avenue also invited to the party two bunnies (Buttercup and Ash), a guinea pig (Thelma), and a beautiful white pony that the little ones took turns riding around the backyard. 
Alexis Bennett, Vogue, 25 Aug. 2022 Her husband, a school principal who has severe eczema, served as the human guinea pig to test her concoctions, and later, her co-founder to join her on this mission. Kimberly Wilson, Essence, 14 Aug. 2022 In 2016, Purdue University announced an income-share agreement program as a guinea pig experiment in which students could get money for college in exchange for a cut of their future earnings. Wired, 13 Aug. 2022 While the 1-year-old guinea pig may not have flaming locks of auburn hair, this brunette beauty has no intention of stealing your man. The Republic, The Arizona Republic, 13 Aug. 2022 Other big names behind the mic include Keanu Reeves (Batman), Olivia Wilde (Lois Lane), Jameela Jamil (Wonder Woman), Marc Maron (Lex Luthor), and Kate McKinnon as Lulu, an evil hairless guinea pig. Lester Fabian Brathwaite, EW.com, 1 Aug. 2022 In a video posted on Instagram, the light brown guinea pig runs back and forth to dunk the 4.4 cm spheres in a tiny hoop. Asha C. Gilbert, USA TODAY, 3 June 2022 The pity party can't last too long, because a guinea pig who once belonged to Lex Luthor, Lulu (Kate McKinnon, completely unleashed), acquires orange kryptonite, giving her extraordinary powers. Brian Lowry, CNN, 28 July 2022 Jacob Hopkins’ path to becoming a human guinea pig wasn’t particularly fraught. Melissa Healy, Los Angeles Times, 30 June 2022 See More
Alexis Bennett, Vogue, 25 Aug. 2022 Her husband, a school principal who has severe eczema, served as the human guinea pig to test her concoctions, and later, her co-founder to join her on this mission. Kimberly Wilson, Essence, 14 Aug. 2022 In 2016, Purdue University announced an income-share agreement program as a guinea pig experiment in which students could get money for college in exchange for a cut of their future earnings. Wired, 13 Aug. 2022 While the 1-year-old guinea pig may not have flaming locks of auburn hair, this brunette beauty has no intention of stealing your man. The Republic, The Arizona Republic, 13 Aug. 2022 Other big names behind the mic include Keanu Reeves (Batman), Olivia Wilde (Lois Lane), Jameela Jamil (Wonder Woman), Marc Maron (Lex Luthor), and Kate McKinnon as Lulu, an evil hairless guinea pig. Lester Fabian Brathwaite, EW.com, 1 Aug. 2022 In a video posted on Instagram, the light brown guinea pig runs back and forth to dunk the 4.4 cm spheres in a tiny hoop. Asha C. Gilbert, USA TODAY, 3 June 2022 The pity party can't last too long, because a guinea pig who once belonged to Lex Luthor, Lulu (Kate McKinnon, completely unleashed), acquires orange kryptonite, giving her extraordinary powers. Brian Lowry, CNN, 28 July 2022 Jacob Hopkins’ path to becoming a human guinea pig wasn’t particularly fraught. Melissa Healy, Los Angeles Times, 30 June 2022 See More Word History
First Known Use
1664, in the meaning defined at sense 1
Kids Definition
guinea pig
noun
: a small stocky South American animal that is a rodent with short ears and a very short tail and is often kept as a pet
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