In the land of device electronics, an intrinsic material is one that is free of impurities and dopants. An intrinsic semiconductor, for instance, would be silicon with impurity concentrations NA = ND = 0 cm-3. Your standard energy band diagram usually pays homage to the virgin material, before it was doped, by displaying the intrinsic Fermi level alongside the Fermi level itself. These are generally denoted Ei and Ef, respectively.