a phosphoprotein that is one of the chief constituents of milk and the basis of cheese: used in plastics, glues, etc.
See casein in American Heritage Dictionary 4
(kāˈsēnˌ, -sē-ĭn)
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.