/ Thesaurus / W Synonyms of willem de sitter Find synonyms for: Noun1. Sitter, Willem de Sitterusage: Dutch astronomer who calculated the size of the universe and suggested that it is expanding (1872-1934)WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: tenacious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language