Wordnet 3.0
NOUN (1)
1.
a vast area of the North Atlantic from the West Indies to the Azores that is dense with gulfweed;
The Collaborative International Dictionary of English v.0.48:
Sargasso \Sar*gas"so\, n. [Sp. sargazo seaweed.] (Bot.)
The gulf weed. See under Gulf.
[1913 Webster]
Sargasso Sea, a large tract of the North Atlantic Ocean
where sargasso in great abundance floats on the surface.
[1913 Webster]
WordNet (r) 3.0 (2006):
Sargasso Sea
n 1: a vast area of the North Atlantic from the West Indies to
the Azores that is dense with gulfweed