WordWeb Online

1. Not contained in or deriving from the essential nature of something
   "an economic theory alien to the spirit of capitalism";
   - foreign
    
2. Being or from or characteristic of another place or part of the world
   "alien customs";
   - exotic

1. A person who comes from a foreign country; someone who does not owe allegiance to your country
   - foreigner, noncitizen, outlander
    
2. Anyone who does not belong in the environment in which they are found
   - stranger, unknown
    
3. A form of life assumed to exist outside the Earth or its atmosphere
   - extraterrestrial being, extraterrestrial, ET

1. Transfer property or ownership
   "The will aliened the property to the heirs";
   - alienate

Derived forms: aliens, aliened, aliening

See also: extrinsic, foreign, strange

Type of: hypothetical creature, interloper, intruder, transfer, traveler [US], traveller [Brit, Cdn], trespasser

Encyclopedia: Alien