marrowbone

from WordNet (r) 3.0 (2006)

marrowbone
    n 1: a bone containing edible marrow; used especially in
         flavoring soup

from The Collaborative International Dictionary of English v.0.48

Marrowbone \Mar"row*bone`\, n.
   A bone containing marrow; pl. ludicrously, knee bones or
   knees; as, to get down on one's marrowbones, i. e., to kneel.
   [1913 Webster]