The Collaborative International Dictionary of English v.0.48:

Vomer \Vo"mer\, n. [L., a plowshare.] (Anat.)
   (a) A bone, or one of a pair of bones, beneath the ethmoid
       region of the skull, forming a part a part of the
       partition between the nostrils in man and other mammals.
   (b) The pygostyle.
       [1913 Webster]

WordNet (r) 3.0 (2006):

vomer
    n 1: thin trapezoidal bone of the skull forming the posterior
         and inferior parts of the nasal septum