The Collaborative International Dictionary of English v.0.48:

Ossify \Os"si*fy\, v. t. [imp. & p. p. Ossified; p. pr. & vb.
   n. Ossifying.] [L. os, ossis, bone + -fy: cf. F. ossifier.
   See Osseous.]
   1. (Physiol.) To form into bone; to change from a soft animal
      substance into bone, as by the deposition of lime salts.
      [1913 Webster]

   2. (Fig.): To harden; as, to ossify the heart. --Ruskin.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Ossifying \Os"si*fy`ing\, a. (Physiol.)
   Changing into bone; becoming bone; as, the ossifying process.
   [1913 Webster]