Webster's Revised Unabridged Dictionary · 1913

Ossify

Ossify , transitive verb

[Latin os, ossis, bone + -fy: compare French ossifier. See Osseous.]

1.
(Physiology) To form into bone; to change from a soft animal substance into bone, as by the deposition of lime salts.
2.
To harden; as, to ossify the heart. [Figurative] — Ruskin

Ossify , intransitive verb

(Physiology) To become bone; to change from a soft tissue to a hard bony tissue.