rennet

/ˈɹɛnɪt/
noun
  1. 1

    An enzyme used as the first step in making cheese, to curdle the milk and coagulate the casein in it, derived by soaking the fourth stomach of a milk-fed calf in brine.

noun
  1. 1

    Any of various kinds of apple, mostly of French origin, characterized by russeting.

Source: https://en.wiktionary.org/wiki/rennet