The Collaborative International Dictionary of English v.0.48:

Shittah \Shit"tah\, Shittah tree \Shit"tah tree`\, n. [Heb.
   shitt[=a]h, pl. shitt[imac]m.]
   A tree that furnished the precious wood of which the ark,
   tables, altars, boards, etc., of the Jewish tabernacle were
   made; -- now believed to have been the wood of the Acacia
   Seyal, which is hard, fine grained, and yellowish brown in
   color.
   [1913 Webster] Shittim

WordNet (r) 3.0 (2006):

shittah tree
    n 1: source of a wood mentioned frequently in the Bible;
         probably a species of genus Acacia [syn: shittah,
         shittah tree]