Organisms living on any other planet but earth, would be aliens... here this should help you.
alien - definition of alien by the Free Online Dictionary, Thesaurus and Encyclopedia.
When we say alien life we don't mean little green men with bowling ball black eye, that fly around and probe people for shits and giggles.
Alien Life literally means Life that didn't originate on Earth. Microorganisms, single cellular organisms, bacteria are all examples of potential Alien Life, aliens don't have to be highly developed species.