The Collaborative International Dictionary of English v.0.48:

Zostera \Zos"te*ra\, n. [NL.] (Bot.)
   A genus of plants of the Naiadaceae, or Pondweed family.
   Zostera marina is commonly known as sea wrack, and
   eelgrass.
   [1913 Webster]

WordNet (r) 3.0 (2006):

Zostera
    n 1: (or in some classifications family Zosteraceae) small genus
         of widely distributed marine plants [syn: Zostera, genus
         Zostera]