What does "forbidden" mean?

Forbidden: Prohibited; interdicted. I kniw no spells, use no forbidden arts. Milton. Forbidden fruit. (a) Any coveted unlawful pleasure, -- so called with reference to the forbidden fruit of the Garden of Eden. (b) (Bot.) A small variety of shaddock (Citrus decumana). The name is given in different places to several varieties of Citrus fruits.