The Collaborative International Dictionary
Matweed
Matweed \Mat"weed`\, n. (Bot.) A name of several maritime grasses, as the sea sand-reed ( Ammophila arundinacea) which is used in Holland to bind the sand of the seacoast dikes (see Beach grass, under Beach); also, the Lygeum Spartum, a Mediterranean grass of similar habit.
Wiktionary
matweed
n. (context botany English) Any of several maritime grasses.