Elodea densa elo·dea·densa uncommon noun 1. aquatic plant with deep green foliage useful to oxygenate an aquarium; sometimes placed in genus Egeria Synonymsdense-leaved elodeaElodea densaEgeria densa Related words Broader terms waterweed WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.