guinea pig
Pluralguinea pigs
- 1The domesticated rodent Cavia porcellus, a small tailless animal often kept as a pet.
Guinea pigs need vitamin C in their diet because they cannot make their own.
Our classroom guinea pig squeaks loudly whenever someone opens the fridge.
Similarcavy
Note
Cavy is the formal name for the same animal, and domestic cavy pins it to the pet rather than its wild relatives. Guinea pig is the word of homes and classrooms; cavy belongs to formal or specialist writing, where the Latin Cavia porcellus may appear beside it.
- 2A living subject used in an experiment or test, especially a person.
Volunteers who serve as guinea pigs in drug trials are usually paid for their time.
No parent wants a child to be a guinea pig for an untested school program.
Similarsubject
Note
The laboratory animal lends its name to anyone tried out on, and the phrase is usually applied to people, hence the common pairing human guinea pig. It takes be, serve as and volunteer as, and it carries a note of risk that test subject lacks: Larry Niven's Ringworld speaks of the unwisdom of volunteering as one. Lab rat is the close synonym.
- 3Any of the tailless rodents of the genus Cavia, which have short ears and look somewhat like large hamsters.
More than one species of wild guinea pig lives in the grasslands and scrub of South America.
Biologists trapped and released wild guinea pigs to count the population in the valley.
Similarcavy
Note
The name gets both halves wrong: the animal is a rodent, not a pig, and its home is South America, not Guinea. Where guinea came from is uncertain. One theory is that the animals reached Europe by way of Guinea, and people took the route for the place of origin.
Less common meanings
- 4A professional company director who sits on boards without the time or the real qualifications for the duties.
Shareholders complained that the board was packed with guinea pigs who asked no questions.
A titled guinea pig lent his name to the prospectus but never attended a single meeting.
Note
This is dated boardroom slang, and the scorn is its point: the speaker is mocking a board, not describing it. In older writing only the setting (prospectuses, shareholders, meetings) separates it from the test subject, which is the meaning a modern reader will reach for first.
- 5A midshipman in the East India service, or, by extension, a seaman of little skill.
The mate cursed the guinea pigs who fumbled the rigging as the squall came on.
A good seaman he is... none of your guinea-pigs.
1748, Tobias Smollett, The Adventures of Roderick RandomNote
At sea the word carried contempt: Smollett's Roderick Random (1748) praises a good seaman as "none of your guinea-pigs", and Macintosh's Travels sets the guinea-pigs beside the mates as the ship's sneering juniors. The East India midshipman came first; calling any clumsy sailor a guinea pig grew out of it. Both writers hyphenate it, as older English did.
Practice
Can you tell the meanings of guinea pig apart? Answer 4 quick questions from this page, or write your own sentence and AI will check it.
Origin
Why the animal is called "guinea" is uncertain: these South American animals may have reached Europe by way of Guinea, "Guinea" may simply stand for any far-off, unknown country, or it may be an alteration of coney ("rabbit"), since Edward Topsell's 1607 treatise on quadrupeds calls them "pig coneys". The figurative sense "experimental subject" is first recorded in the early 20th century, with examples from 1913 and 1920, and comes from the long use of guinea pigs in scientific research.