Breadcrumb Home > Thesaurus > O Synonyms of onset Find synonyms for: Noun 1. onset, oncoming, start usage: the beginning or early stages; "the onset of pneumonia" 2. attack, onslaught, onset, onrush, operation, military operation usage: (military) an offensive against an enemy (using weapons); "the attack began at dawn" WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of onset (Dictionary) TrendingHere are the facts and trivia that people are buzzing about. Jewish Holidays, 2010-2030 (A.M. 5770-5791) Western Christian Holidays, 2010-2030 12 Steps to a New Year New Year's Resolution to Slim Down? Martin Luther King Speeches Books of the Bible: Old Testament Books in Order ✖ Related Content Daily Word Quiz: saturnine Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language