The word "extrasolar" means something that is located or exists beyond our solar system, specifically referring to objects like planets or stars that are found in other star systems outside of our own. Full definition
The HDST could finally answer the question of whether humans are alone in the Universe, by directly probing the atmospheres of dozens of extrasolar planets for signs of life. (scientificamerican.com)
Atmospheres of extrasolar planets in the super-Earth era. (sciencenews.org)
«Now that we have some hold on what the original moons of Neptune were like, that can give us some clue as to what we should expect for extrasolar planets of that type,» says Matija Cuk at the SETI Institute. (newscientist.com)