The point at which you drink so much alcohol, that basic body functions become difficult, near to impossible to perform. Examples include: not being able to talk coherently, inability to stand or walk, falling face first, etc.
Dovered is one of the upper echelons of intoxication. It is right under unconsciousness, but well above hammered or plowed.
Friend 1: "Hey man, did you see Mark last night? That boy was drunk as hell"
Friend 2: "Naww man, with how many times he fell down, he was Dovered"