Source : Webster's Revised Unabridged Dictionary (1913)

Zostera \Zos"te*ra\, n. [NL.] (Bot.)
   A genus of plants of the {Naiadace[ae]}, or Pondweed family.
   {Zostera marina} is commonly known as {sea wrack}, and
   {eelgrass}.

Eelgrass \Eel"grass`\, n. (Bot.)
   A plant ({Zostera marina}), with very long and narrow leaves,
   growing abundantly in shallow bays along the North Atlantic
   coast.

Source : WordNet®

Zostera marina
     n : submerged marine plant with very long narrow leaves found in
         abundance along North Atlantic coasts [syn: {eelgrass}, {grass
         wrack}, {sea wrack}]