nipple

noun

• 1the small projection in which the mammary ducts of female mammals terminate and from which milk can be secreted.
• the vestigial structure in a male that corresponds to the nipple of a female mammal.
• North American the teat of a feeding bottle: it is crucial to remove the cap or nipple of the baby’s bottle before heating

• 2a small projection on a device, especially one from which oil or other fluid is dispensed: the centralized greasing point comprises a bank of seven nipples
• a short section of pipe with a screw thread at each end for coupling: install a threaded nipple between the valve outlet and the shut-off inlet