guinea pig guinea pig /ˈɡɪni pɪg/

noun

1. Stout-bodied nearly tailless domesticated cavy; often kept as a pet and widely used in research  ( Cavia cobaya , guinea pig )
   stout-bodied nearly tailless domesticated cavy; often kept as a pet and widely used in research
   
   
2. A person who is subjected to experimental or other observational procedures; someone who is an object of investigation  ( guinea pig , subject , case )
   a person who is subjected to experimental or other observational procedures; someone who is an object of investigation
    The subjects for this investigation were selected randomly
   the subjects for this investigation were selected randomly
    The cases that we studied were drawn from two different communities
   the cases that we studied were drawn from two different communities