1) Plant common name 2) Seaweed 
Seagrasses are flowering plants (Division Angiospermae) belonging to four plant families (Posidoniaceae, Zosteraceae, Hydrocharitaceae, or Cymodoceaceae), all in the order Alismatales (in the class of monocotyledons), which grow in marine, fully saline environments. There are 12 genera with some 58 species known. ==Ecology== These unusual marine f...
[n] - any of various seaweeds that grow underwater in shallow beds
type of ocean plant with grass-like features
noun any of various seaweeds that grow underwater in shallow beds; `seagrass provides a protective environment in which young fish can develop`