Un-earthly means something that is strange, out of this world, or supernatural. The antonyms for un-earthly are terrestrial, earthly, natural, normal, and mundane. Terrestrial refers to anything that belongs or is related to Earth, including its inhabitants and nature. Earthly means something that is worldly, material, or physical. Natural means something that follows the laws of nature or the natural world. Normal refers to something that is ordinary or customary. Mundane means something that is routine, ordinary, or boring. All these antonyms signify the opposite of un-earthly, which is anything that is considered weird or beyond human comprehension.