1. (n.) The protuberance through which milk is drawn from the breast or mamma; the mammilla; a teat; a pap.

2. (n.) The orifice at which any animal liquid, as the oil from an oil bag, is discharged.

3. (n.) 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. (n.) A pipe fitting, consisting of a short piece of pipe, usually provided with a screw thread at each end, for connecting two other fittings.

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