Waking up with an erection. It's often associated with the need to use the bathroom upon waking up. Scientific term is nocturnal penile tumescence. There is no real scientific proof as to why men wake up with a erection although there are many theories. And by the way "dr. Pascalle" is a fake and an idiot. No such thing as hypervasodilation.
Means the same thing as Morning Glory
It sucks trying to take a piss when you got a morning wood.