Source : Webster's Revised Unabridged Dictionary (1913)

Sea moss \Sea" moss`\ (?; 115). (Zo["o]l.)
   Any branched marine bryozoan resembling moss.

Source : WordNet®

sea moss
     n 1: sessile aquatic animal forming mosslike colonies of small
          polyps each having a curved or circular ridge bearing
          tentacles; attach to stones or seaweed and reproduce by
          budding [syn: {bryozoan}, {polyzoan}, {sea mat}, {moss
          animal}]
     2: any of various red algae having graceful rose to purple
        fronds (e.g. dulse or carrageen)