PS: Dracolich refers to a lich not a normal undead. Huge difference because Liches would have Activated abilities at least.
I believe the term "Dracolich" can also refer to a Dragon Zombified by a lich, regardless of whether the creature is or isn't a lich itself.
Either way though, it has come to be a more general term for undead dragons than it probably should be.
I have never seen a non lich undead dragon referred to correctly as a Dracolich regardless of the source of the animation.
This said many liches have been written to create subservient liches so the author can prove that This Lich is much worse than a regular lich.