A sexual act in which one person shoots jizz (a protein shot) into the other's mouth and then shake their head vigorously.
Gwen: "Let's get out of here and grab a beer."
Richard: "Are you insane? You know my midterm and finals ritual. I study til 11, 9 solid hours of sleep, protein shake in the morning."
(from 'Van Wilder')
In the world of strength-athleticism, supplements for growth are often used. Protein shakes are powedered substances which are mixed with milk, oragange juice etc. to produce a drink apporoximately 70% protein.
consumed after exercise, the protein rebuilds the muscle bigger and stronger.