/ Thesaurus / O Synonyms of outer planet Find synonyms for: Noun1. outer planet, planet, major planetusage: (astronomy) a major planet whose orbit is outside the asteroid belt (Jupiter, Saturn, Uranus, Neptune, Pluto)WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: exemplary Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language