class Phaeophyceae classp·haeop·hy·ceae uncommon noun 1. brown algae; mostly marine and littoral eukaryotic algae SynonymsPhaeophyceaeclass Phaeophyceae Related words Broader terms class Parts Phaeophyta Part of brown algaeLaminarialesFucales WordNet 2.1 (Princeton University). WordNet 2.1 Copyright Princeton University. All rights reserved.