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Meaning of guinea pig

guin'ea pig"

Pronunciation: [key]
  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. the subject of any sort of experiment.
Random House Unabridged Dictionary, Copyright © 1997, by Random House, Inc., on Infoplease.