/ Thesaurus / S Synonyms of south island Find synonyms for: Noun1. South Islandusage: the larger but less populous of two main islands of New Zealand; separated from North Island by Cook StraitWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: loathe Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language