The Collaborative International Dictionary of English v.0.48:

Ossification \Os`si*fi*ca"tion\, n. [Cf. F. ossification. See
   Ossify.]
   1. (Physiol.) The formation of bone; the process, in the
      growth of an animal, by which inorganic material (mainly
      lime salts) is deposited in cartilage or membrane, forming
      bony tissue; ostosis.
      [1913 Webster]

   Note: Besides the natural ossification of growing tissue,
         there is the so-called accidental ossification which
         sometimes follows certain abnormal conditions, as in
         the ossification of an artery.
         [1913 Webster]

   2. The state of being changed into a bony substance; also, a
      mass or point of ossified tissue.
      [1913 Webster]

WordNet (r) 3.0 (2006):

ossification
    n 1: the developmental process of bone formation
    2: the calcification of soft tissue into a bonelike material
    3: the process of becoming rigidly fixed in a conventional
       pattern of thought or behavior
    4: hardened conventionality [syn: ossification, conformity]