- The protuberance through which milk is drawn from the
breast or mamma; the mammilla; a teat; a pap. - The orifice at which any animal liquid, as the oil from an
oil bag, is discharged. - Any small projection or article in which there is an
orifice for discharging a fluid, or for other purposes; as, the nipple
of a nursing bottle; the nipple of a percussion lock, or that part on
which the cap is put and through which the fire passes to the charge. - A pipe fitting, consisting of a short piece of pipe,
usually provided with a screw thread at each end, for connecting two
other fittings.