Name given to several breeds of pedigree cat, related to the siamese and oriental families; their primary feature is that they are hairless. Although there are records of earlier hairless cats, the strains at the moment are mainly descended from spontaneously occurring (mutant, if you prefer) litters of hairless cats born in Toronto in the 1960s (Canadian Sphinx) and Russia in the 1980s (Don and St Petersburg sphinxes); the breeding progams involve crossbreeding with orientals, siamese and European shorthairs.
Sphinxes have a reputation as affectionate and lively pets and do not suffer from fleas or cause a reaction amongst most cat allergy sufferers, but require more care than a normal cat and can suffer from both the cold and sunburn; their somewhat bizarre appearance is considered ugly in some quarters, and there are some animal rights arguments against the deliberate breeding of an animal breed which is only viable in symbiosis with humans.
Apparently spelt sphynx in the USA, because they have, like, more logical spelling and stuff there, and might otherwise get confused with colossal noseless statues.