Source : Webster's Revised Unabridged Dictionary (1913)

Deadwood \Dead"wood`\, n.
   1. (Naut.) A mass of timbers built into the bow and stern of
      a vessel to give solidity.

   2. Dead trees or branches; useless material.

Source : WordNet®

deadwood
     n 1: a branch or a part of a tree that is dead
     2: someone or something that is unwanted and unneeded [syn: {fifth
        wheel}]