The
act of using a sauce or other such condiment just before
passing it to the person who has requested it. The highjacking of
said sauce en route to its destination.
"Dave, could you pass me the
gravy please?"
"Of course, my dear."
Dave picks up the gravy boat, but pours some onto his
plate first
"Oi, you cheeky fucker!
Stop saucejacking and pass it here right now!"