Noun guinea pig has 2 senses
- subject, case, guinea pig - 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 cases that we studied were drawn from two different communities"
--1 is a kind of person, individual, someone, somebody, mortal, human, soul
- guinea pig, Cavia cobaya - stout-bodied nearly tailless domesticated cavy; often kept as a pet and widely used in research
--2 is a kind of cavy