The Collaborative International Dictionary of English v.0.48:

Logwood \Log"wood`\n. [So called from being imported in logs.]
   The heartwood of a tree (H[ae]matoxylon Campechianum), a
   native of South America, It is a red, heavy wood, containing
   a crystalline substance called h[ae]matoxylin, and is used
   largely in dyeing. An extract from this wood is used in
   medicine as an astringent. Also called Campeachy wood, and
   bloodwood.
   [1913 Webster]

WordNet (r) 3.0 (2006):

logwood
    n 1: very hard brown to brownish-red heartwood of a logwood
         tree; used in preparing a purplish red dye
    2: spiny shrub or small tree of Central America and West Indies
       having bipinnate leaves and racemes of small bright yellow
       flowers and yielding a hard brown or brownish-red heartwood
       used in preparing a black dye [syn: logwood, logwood
       tree, campeachy, bloodwood tree, Haematoxylum
       campechianum]