guinea pig

noun5

1. •
   Any tailless rodent of the genus Cavia, which have short ears and superficially resemble large hamsters.
2. •
   A domestic guinea pig, Cavia porcellus, often kept as a pet.
3. •
   (figurative) A living experimental subject.

   • He became a human guinea pig and was paid by the company.
4. •
   (slang, old-fashioned) A professional company director, without time or real qualifications for the duties.
5. •
   (no longer used) A midshipman in the East India service; (by extension) a low-skilled or non-proficient seaman.

   • A good seaman he is... none of your guinea-pigs. — 1748