Terrestrial refers to things have to do with the land or the Earth. Related terms Terrestrial animal,an animal that lives on land opposed to living in water. * Terrestrial plant, a plant that grows on land rather than in water or on rocks or trees Terrestrial planet, a planet that's primarily composed of silicate rocks. These planets go from Mercury to Mars. They are very small compared to the Jovian planets. They all have an iron core and contain not much gas Terrestrial ecoregion, land ecoregi… (More on Terrestrial)