Pre-morning wood.
While still sleeping girlfriend notices you have an erection.

Large, beautiful breasts that are keep well consealed and initially appear to be much smaller and less impressive than they actually are until unleashed.

alternate term for "morning wood"

Slumber lumber is another euphemism for waking up with an erection- otherwise known as 'morning wood'.

A more sophisticated version of morning wood. Usually when you are fully asleep, and the blood can add extra power.