The Collaborative International Dictionary of English v.0.48:

Dulse \Dulse\ (d[u^]ls), n. [Cf. Gael. duileasg; duille leaf +
   uisge water. Cf. Whisky.] (Bot.)
   A seaweed of a reddish brown color, which is sometimes eaten,
   as in Scotland. The true dulse is Sarcophyllis edulis; the
   common is Rhodymenia. [Written also dillisk.]
   [1913 Webster]

         The crimson leaf of the dulse is seen
         To blush like a banner bathed in slaughter. --Percival.
   [1913 Webster]

WordNet (r) 3.0 (2006):

dulse
    n 1: coarse edible red seaweed [syn: dulse, Rhodymenia
         palmata]