Mammequin

A female mannequin that's been shaped to have an outrageously huge rack. Double D tittows at minimum. Often placed in the front window of a smut shop and dressed in naughty school girl or Sailor Moon whorewear to show off the merchandise for passersby. Most guys would seriously consider banging one of these things if given the chance...

A guy and his flat-chested girl walk by the local Triple X Emporium when she sees him eyeballing a large breasted display dummy.
Girlfriend: "Were you just lusting over that slut nurse in the window?!"
Guy: "What? Uh...hell no, baby, I wasn't eyeing that mammequin at all, just the outfit! I was thinking how hot it would look on you!"
Girl sighs contentedly as Guy wonders if banging a mammequin's illegal...