from The American Heritage® Dictionary of the English Language, 4th Edition
- adj. Originating, located, or occurring outside Earth or its atmosphere: intelligent extraterrestrial life.
- n. An extraterrestrial being or life form.
from Wiktionary, Creative Commons Attribution/Share-Alike License
- adj. Originating from outside of the Earth's atmosphere, from space, or from another planet; alien to Earth or its environment.
- n. A being originating from outside of the Earth's atmosphere, from space, or from another planet; an alien
from the GNU version of the Collaborative International Dictionary of English
- adj. originating or located or occurring outside Earth or its atmosphere.
- n. a hypothetical form of life existing outside the Earth or its atmosphere, especially intelligent life on other planets or in other solar systems.
from The Century Dictionary and Cyclopedia
- Occurring outside of the earth; extramundane.
from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.
- n. a form of life assumed to exist outside the Earth or its atmosphere
- adj. originating or located or occurring outside Earth or its atmosphere
extra- + terrestrial (Wiktionary)