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guinea pig

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noun
  1. a short-eared, tailless rodent of the genus Cavia, usually white, black, and tawny, commonly regarded as the domesticated form of one of the South American wild species of cavy: often used in scientific experiments or kept as a pet.
  2. Informal. the subject of any sort of experiment.
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Origin of guinea pig

First recorded in 1655–65
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2018

Examples from the Web for guinea pig

Historical Examples

  • Well, my opinion of him is that he is merely a guinea-pig—you know what that is?

    A Woman Intervenes

    Robert Barr

  • This is a quite peculiar group, characteristic for the blood of the guinea-pig.

  • The capybara is classed with the Cavidae or guinea-pig tribe.

    The Western World

    W.H.G. Kingston

  • You will have to take the guinea-pig box out of your room under the eaves.

    True to His Home

    Hezekiah Butterworth

  • The guinea-pig is not a pig, nor does it come from Guinea (see p. 51).

British Dictionary definitions for guinea pig

guinea pig

noun
  1. a domesticated cavy, probably descended from Cavia porcellus, commonly kept as a pet and used in scientific experiments
  2. a person or thing used for experimentation
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Word Origin

C17: origin uncertain: perhaps from old use of the name Guinea to mean any remote unknown land
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Word Origin and History for guinea pig

1660s, native to South America and perhaps so called either because it was first brought back to Britain aboard Guinea-men, ships that plied the triangle trade between England, Guinea, and South America [Barnhart, Klein]; or from confusion of Guinea (q.v.) with the South American region of Guyana (but OED is against this). In the extended sense of "one subjected to an experiment" it is first recorded 1920, because they were commonly used in vivisection experiments.

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Online Etymology Dictionary, © 2010 Douglas Harper
guinea pig in Medicine

guinea pig

(gĭn′ē)
n.
  1. Any of various small, short-eared domesticated rodents of the genus Cavia, having variously colored hair and no visible tail. They are widely kept as pets and often used as experimental animals.
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The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.