Breadcrumb Home > Thesaurus > O Synonyms of ontario Find synonyms for: Noun 1. Lake Ontario, Ontario usage: the smallest of the Great Lakes 2. Ontario usage: a prosperous and industrialized province in central Canada WordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved.Definition and meaning of ontario (Dictionary) TrendingHere are the facts and trivia that people are buzzing about. Hanukkah Origins of the Christmas Holiday Jewish Holidays, 2010-2030 (A.M. 5770-5791) Western Christian Holidays, 2010-2030 Krampus: The Christmas Devil Kwanzaa ✖ Related Content Daily Word Quiz: dissemble Analogy of the Day: Today’s Analogy Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language