Nipple /(nĭp"p'l)/

Nip·ple

Nipple

n.
  1. The protuberance through which milk is drawn from the breast or mamma; the mammilla; a teat; a pap. (Anat.)
  2. The orifice at which any animal liquid, as the oil from an oil bag, is discharged. [R.]
  3. 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.
  4. A pipe fitting, consisting of a short piece of pipe, usually provided with a screw thread at each end, for connecting two other fittings. (Mech.)

Phrases & Compounds
Solder nipple
a short pipe, usually of brass, one end of which is tapered and adapted for attachment to the end of a lead pipe by soldering.