noun
(anatomy) The projection of a mammary gland from which, on female therian mammals, milk is secreted.
The nipple (definition 1) and the areola together.
A mechanical device through which liquids or gases can be passed in a regulated manner.
An artificial nipple (definition 1) used for bottle-feeding infants.
Any small physical protrusion, such as the lumps on the F and J keys on computer keyboards.
Any small physical protrusion on an automotive, a machine part or any other part that fits into a groove on another part.
(now chiefly historical) A perforated segment that fits into part of the breech of a muzzle-loading gun, on which the percussion cap is fixed.
(plumbing, chiefly US) A short tube threaded at both ends, used as a connector.
(cycling) An internally threaded piece which holds a bicycle spoke in place on the rim.
(computing, humorous) A pointing stick.
verb
(transitive) To fit (a baby's bottle, etc.) with a nipple.
(transitive) To give one's nipple to (a baby) to allow breastfeeding.