n. [ AS. rinnan, rennan, to run, cf. gerinnan to curdle, coagulate. √11. See Run, v. ] 1. The inner, or mucous, membrane of the fourth stomach of the calf, or other young ruminant. [ 1913 Webster ]

2. an infusion or preparation of the calf stomach lining, used for coagulating milk. The active principle in this coagulating action is the enzyme rennin. [ Written also runnet. ] [ 1913 Webster +PJC ]

Cheese rennet. (Bot.) See under Cheese. --
Rennet ferment (Physiol. Chem.), the enzyme rennin, present in rennet and in variable quantity in the gastric juice of most animals, which has the power of curdling milk. The enzyme presumably acts by changing the casein of milk from a soluble to an insoluble form. --
Rennet stomach (Anat.), the fourth stomach, or abomasum, of ruminants. [ 1913 Webster +PJC ]

n. [ F. rainette, reinette, perhaps fr. raine a tree frog, L. rana, because it is spotted like this kind of frog. Cf. Ranunculus. ] (Bot.) A name of many different kinds of apples. Cf. Reinette. Mortimer. [ 1913 Webster ]

a. Provided or treated with rennet. [ R. ] “Pressed milk renneted.” Chapman. [ 1913 Webster ]

n. (Bot.) Same as 1st Rennet. [ 1913 Webster ]