The definition of terrestrial planets is.. they are planets that are solid rock or metal.in our solar system, the terrestrial planets are the four inner planets. Our inner planets are Mercury, Venus, Earth, and Mars. Terrestrial planets are also known as Telluric or Rocky planets. The term “Terrestrial” is made of Latin word for Earth “Terra”. That is why terrestrial planets are also called “Earth-like” planets, due to the similarity in the structure of the planet Earth.
