genus Sium ge·nus·sium uncommon noun 1. perennial of wet and marshy places in the northern hemisphere: water parsnips SynonymsSiumgenus Sium Related words Broader terms rosid dicot genus Parts Umbelliferae Part of water parsnipgreater water parsnipskirret WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.
