1. A projection occurring in various animal tissues and organs.
2. A small blunt hair on plants.
3. Any small, nipplelike process or projection.
4. One of certain small protuberances concerned with the senses of touch, taste, and smell; such as, the papillae of the tongue.
5. A small vascular process at the root of a hair.
6. A papule or pimple.

1. The protuberance through which milk is drawn from the breast or mamma; the mammilla; a teat; a pap.
2. The orifice at which any animal liquid is discharged; such as, the oil from an oil bag.
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; or the nipple of a percussion lock.