As defined in the Peaches song "Slippery Dick", a sauce licker (or, as Peaches pronounces it: "saws leekur")is someone who enjoys licking or lapping up the oozing contents of an orifice after sex. Orifices in question can be the mouth, the vagina, the asshole, or even the hole at the end of the penis's shaft.
"Jenna is such a sauce licker! She took Will's penis and licked up the semen after jacking him off! The day before she was persuaded by Dennee to lick the cum out of his asshole after Jeremiah blew his load in his rectum. Then Doug came by and swapped a load of Andrew's semen with Jenna via the mouth. Later that night, Kaite came over and let Jenna lick the lady juice from her snatch."