The Collaborative International Dictionary of English v.0.48:

bonemeal \bone"meal`\ n.
   ground bones, used as a fertilizer or as a component in
   animal feed; -- it is high in phosphate content.
   [WordNet 1.5 +PJC]

WordNet (r) 3.0 (2006):

bonemeal
    n 1: fertilizer made of ground bones