A fork of Rural Dictionary
The weird, liquid-y stuff that comes out of a ketchup bottle if you don't shake it.
"You gotta shake dat ketchup bottle, or else ketchup pre-cum will be all over your hot dog."
The watery bit of ketchup that comes out when you go to use the ketchup but the bottle hasn't been shaken up or it has been left a while without being used. This leads to a puddle of watery ketchup being left seeping onto your plate and probably on your hands.
"Ew, I forgot to shake the bottle, now there's Pre Ketchup on my chips."
"Don't forget to shake the bottle or you'll get Pre Ketchup."