/ Thesaurus / A Synonyms of alga Find synonyms for: Noun1. alga, algae, protoctistusage: primitive chlorophyll-containing mainly aquatic eukaryotic organisms lacking true stems and roots and leavesWordNet 3.0 Copyright © 2006 by Princeton University. All rights reserved. Related Content Daily Word Quiz: nefarious Analogy of the Day: Today’s Analogy Spelling Bee: Today’s Spelling Bee Frequently Misspelled Words Frequently Mispronounced Words Easily Confused Words Writing & Language