Source : Webster's Revised Unabridged Dictionary (1913)

Sea wrack \Sea" wrack`\ (Bot.)
   See {Wrack}.

Source : WordNet®

sea wrack
     n 1: submerged marine plant with very long narrow leaves found in
          abundance along North Atlantic coasts [syn: {eelgrass},
          {grass wrack}, {Zostera marina}]
     2: growth of marine vegetation especially of the large forms
        such as rockweeds and kelp [syn: {wrack}]