Seized, = frozen, stuck, unable to turn. As in the engine seized from lack of oil.
Sounds like something that is suppose to be turning is not. If you can figure how to loosen the belt tension you can check most of the components for rotation.
Alternator should spin freely
Power steering should spin fairly easy
AC should also spin fairly easy
Water pump should turn fairly easy also
If one or more of these are hard to turn it could be the problem.
If you can not identify even one of the components listed above then you shouldnt even open the hood. Just drive the squealing hog to the nearest dealer or repair shop.