/ Thesaurus / P Synonyms of planetesimal hypothesis Find synonyms for: Noun1. planetesimal hypothesis, scientific theoryusage: (cosmology) the theory that the solar system was formed by the gravitational accumulation of planetesimalsWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: feline Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language