[PIG] an animal with pink, black or brown skin, short legs, a broad nose and a short tail which curls round itself. Pigs are kept on farms for their meat (called pork ) or live in the wild
[SHEEP] An animal with a thick coat, kept on farms for its meat (called mutton or lamb)
Collins COBUILD Dictionary 2006
[PIG] A pig is a pink or black animal with short legs and not much hair on its skin. Pigs are often kept on farms for their meat, which is called pork, ham, bacon, or gammon.
[SHEEP] A sheep is a farm animal which is covered with thick curly hair called wool. Sheep are kept for their wool or for their meat.