n. A protuberance of the breast where, in the female, the galactophorous ducts discharge; a pap; a teat.n. The papilla by which any animal secretion is discharged.n. Anything that projects like a nipple, as the projecting piece in a gun or a cartridge upon which the percussion-cap is placed to be struck by the hammer, the mouthpiece of a nursing-bottle, a nipple-shield, etc.n. A reducing-coupling for hose or for joining a hose to a pipe.n. A hollow piece projecting from and forming a passage connecting with the interior of a metal pipe, used for the attachment of a faucet or cock.To furnish with a nipple or nipples; cover with nipple-like protuberances.