outer planet

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun astronomy Any planet of the Solar System whose orbit is located beyond the asteroid belt, i.e., any of Jupiter, Saturn, Uranus, or Neptune.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (astronomy) a major planet whose orbit is outside the asteroid belt (Jupiter, Saturn, Uranus, Neptune, Pluto)