Fossilize \Fos"sil*ize\, v. t. [imp. & p. p. {Fossilized}; p. pr. & vb. n. {Fossilizing}.] [Cf. F. fossiliser.] 1. To convert into a fossil; to petrify; as, to fossilize bones or wood. 2. To cause to become antiquated, rigid, or fixed, as by fossilization; to mummify; to deaden. Ten layers of birthdays on a woman's head Are apt to fossilize her girlish mirth. --Mrs. Browning.