A prosthesis of a Ferengi lobe.
Lobe is a Ferengi term referring alternately to the rims of their ears, and in a colloquial sense, the business acumen of an individual Ferengi. The expression may represent customary Ferengi sexism, as Ferengi women have smaller lobes than men, and were formerly forbidden to participate in business.
Physically, the lobes are a highly sensitive area; they are an erogenous zone that produce feelings of pleasure and contentment when stroked, as in oo-mox, but are also very sensitive to pain. (DS9: "Family Business")
Ferengi will often use lobes to emphasize the intelligence, or lack of it, of a particular business maneuver. Quark regularly told Rom that he didn't have the lobes for business. (DS9: "The Nagus") They could also use this distinction on alien species they encountered - in 2151, while pillaging Enterprise, the marauders Muk and Grish encountered the Earth dog, Porthos; when their universal translators failed to turn its barking into spoken word, Muk concluded that the animal was a lower life-form, possibly a food source, but Grish, noting the creature's unusually large ears, wasn't so sure. (ENT: "Acquisition")
Nog told Jake Sisko during a card game that everytime a Ferengi lobe was tingeling there was an opportunity. (DS9: "Progress")
Quark explained the term to Karemma Minister Hanok in 2372. (DS9: "Starship Down")