From Online Dictionary of Crystallography
Polyamorphisme (Fr). Polyamorphie (Ge). Poliamorfismo (It). Poliamorfismo (Sp).
The phenomenon in which the same chemical compound exhibits different amorphous modifications. Polyamorphism is the analogous of polymorphism for crystalline materials.
Polyamorphism requires the existence of two (or more) different amorphous modifications with discontinuous (first-order) transition between them. When such a transition occurs between two stable liquid states, one speaks of liquid–liquid phase transition.