1 a small projection in which the mammary ducts of either sex of mammals terminate and from which in females milk is secreted for the young.
2 the teat of a feeding-bottle.
3 a device like a nipple in function, e.g. the tip of a grease-gun.
4 a nipple-like protuberance.
5 US a short section of pipe with a screw-thread at each end for coupling.
Etymology: 16th c., also neble, nible, perh. dimin. f. neb
Useful english dictionary. 2012.