What is the definition of the Earth's mantle?

The Earth's mantle is the thickest layer of the planet and accounts for about 84% of the Earth's volume and 67% of its mass. It lies between the crust and the core. The mantle begins at the boundary known as the Mohorovicic discontinuity and extends down to the core-mantle boundary, which is also called the Gutenberg discontinuity. read more

Earth's mantle is a silicate rocky shell with an average thickness of 2,886 kilometres (1,793 mi). The mantle makes up about 84% of Earth's volume. It is predominantly solid but in geological time it behaves as a viscous fluid. read more