Entry 1 sense Webster, 1913 Phycoerythrin · Phy·co·e·ryth·rin · IPA /ˌfaɪkəʊ.iˈɹɪθɹɪn/ 01 n. A red coloring matter found in algae of the subclass Florideae. 1. A red coloring matter found in algae of the subclass Florideae.