The act of eking one's seed out from the testes. Ejaculating. Spunking up a storm in a lady's teacup. Cleaning one's pipes.
Farquar's hand was a blur as he frantically, desperately reached the point of no return. "By Jove, I think it is time to empty one's sack" he ejaculated, plum firmly in his mouth, and with a gruff grunt of pleasure, he emptied his sack onto the shiny, firm booty that was splayed before him.