gulfweed

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. Any of several brownish seaweeds of the genus Sargassum of tropical Atlantic waters, having rounded air bladders and often forming dense, floating masses. Also called sargasso, sargassum.

Century Dictionary and Cyclopedia

1. n. A coarse olive seaweed, Sargassum bacciferum, belonging to the suborder Fucaceæ. It has its specific name from the numerous grape-like air-vessels by which it is buoyed. It was first discovered by Columbus. S. vulgare is also sometimes called gulfweed. Gulfweed grows attached in the West Indies, where it fruits, and is found floating and infertile in the course of the Gulf Straam and in the Sargasso sea (a tract of water so called from the masses of floating gulfweed in it, sometimes so dense as to impede navigation), from latitude 20° to 45° N. Farlow, Marine Algæ of New England. Also called driftweed.

GNU Webster's 1913

1. n. a branching seaweed (Sargassum bacciferum, or sea grape), having numerous berrylike air vessels, -- found in the Gulf Stream, in the Sargasso Sea, and elsewhere.
2. n. A brown seaweed (Sargassum bacciferum) with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea.

WordNet 3.0

1. n. brown algae with rounded bladders forming dense floating masses in tropical Atlantic waters as in the Sargasso Sea