fossilise

/F AA1 S AH0 L AY0 Z/
verb
  1. 1

    To make into a fossil

  2. 2

    To become a fossil

  3. 3

    (by extension) to become inflexible or outmoded

  4. 4

    (by extension) To make antiquated, rigid, or fixed; to deaden.

Source: https://en.wiktionary.org/wiki/fossilise, https://en.wiktionary.org/wiki/fossilize