oarweed
Concise Oxford English Dictionary © 2008 Oxford University Press:
oarweed/ˈɔːwiːd/
▶noun a large brown kelp (seaweed) with a long hard stalk and a large oar-shaped frond divided into ribbon-like strips, growing on rocky shores. [Genus Laminaria.]
'oarweed' also found in these Oxford entries:

