Meat of sheep is known as

Meat of sheep is known as Mutton.
Lamb is 'a young sheep', or 'meat from a young sheep', while mutton is defined as 'meat from a fully grown sheep'.
Lamb, hogget, and mutton, generically sheep meat, are the meat of domestic sheep. A sheep in its first year is a lamb and its meat is also lamb. The meat from sheep in their second year is hogget. Older sheep meat is mutton. Mutton is meat from a sheep over two years old, and has less tender flesh. In general, the darker the colour, the older the animal.