Alien

Alien is a broad, subjective term, which can be applied as both a noun and an adjective, for any entity, object, place or practice which is not familiar. When referring to entities, this can be used to describe both sentient and non-sentient organic creatures, as well as robots. In most occurrences, this means entities which are not native to Earth and thus are considered "alien" from the viewpoint of the human race. However, to any species not native to Earth, a human would be considered alien.