Source : Webster's Revised Unabridged Dictionary (1913)

Sea mat \Sea" mat`\ (Zo["o]l.)
   Any bryozoan of the genus {Flustra} or allied genera which
   form frondlike corals.

Source : WordNet®

sea mat
     n : 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 moss}, {moss
         animal}]