noun.
A white, tasteless, odorless protein precipitated from milk by rennin. It is the basis of cheese and is used to make plastics, adhesives, paints, and foods.
The Century Dictionary and Cyclopedia
noun.
The chief nitrogenous ingredient of milk.
the GNU version of the Collaborative International Dictionary of English
noun.
A proteid substance present in both the animal and the vegetable kingdom. In the animal kingdom it is chiefly found in milk, and constitutes the main part of the curd separated by rennet; in the vegetable kingdom it is found more or less abundantly in the seeds of leguminous plants. Its reactions resemble those of alkali albumin.