The Collaborative International Dictionary of English v.0.48:

Redwood \Red"wood`\ (-w[oo^]d`), n. (Bot.)
   (a) A gigantic coniferous tree (Sequoia sempervirens) of
       California, and its light and durable reddish timber. See
       Sequoia.
   (b) An East Indian dyewood, obtained from Pterocarpus
       santalinus, Caesalpinia Sappan, and several other
       trees.
       [1913 Webster]

   Note: The redwood of Andaman is Pterocarpus dalbergioides;
         that of some parts of tropical America, several species
         of Erythoxylum; that of Brazil, the species of
         Humirium.
         [1913 Webster]

WordNet (r) 3.0 (2006):

redwood
    n 1: the soft reddish wood of either of two species of sequoia
         trees
    2: either of two huge coniferous California trees that reach a
       height of 300 feet; sometimes placed in the Taxodiaceae [syn:
       sequoia, redwood]