Source : Webster's Revised Unabridged Dictionary (1913)

Balsa \Bal"sa\, n. [Sp. or Pg. balsa.] (Naut.)
   A raft or float, used principally on the Pacific coast of
   South America.

Source : WordNet®

balsa
     n 1: strong lightweight wood of the balsa tree used especially
          for floats [syn: {balsa wood}]
     2: forest tree of lowland Central America having a strong very
        light wood; used for making floats and rafts and in crafts
        [syn: {Ochroma lagopus}]