The hypothetical device that over-made-up women must have used in order to apply the monstrous pile of caked-on colour to their face.
It refers to the Simpsons episode in which Homer invented such a device, which, after applied to his wife Marge, elicited the reply: "Homer! You've got it set on whore!"
Damn, girl, you look like a clown. Put down the make-up shotgun next time.