nipple

noun

1. The projection of a mammary gland from which, on female therian mammals, milk is secreted.

   “Mary felt annoyed at the girl; just because bras had become passé, did a girl with so pronounced a bosom have to cater to fashion? In this case practicality dictated a bra, and Mary stood at the desk feeling herself flushing with disapproval. And artificial nipple-dilation; it was just too much.”

2. The nipple (definition 1) and the areola together.

   “Joan Trieste wore skin-tight dark pants and slippers and a cotton man’s-style shirt; as far as he could tell, she had on no bra, as fashion dictated, but her nipples were merely flat dark circles beneath the white cotton fabric of her shirt: she could not afford or did not care to have the currently-popular dilation operation.”

3. A mechanical device through which liquids or gases can be passed in a regulated manner.
4. An artificial nipple (definition 1) used for bottle-feeding infants.
5. Any small physical protrusion, such as the lumps on the F and J keys on computer keyboards.
6. Any small physical protrusion on an automotive, a machine part or any other part that fits into a groove on another part.
7. (historical)A perforated segment that fits into part of the breech of a muzzle-loading gun, on which the percussion cap is fixed.

   “I could tell he didn't agree but he went to the corner and took up his squirrel gun, feeling the nipple for a percussion cap.”

8. (US)A short tube threaded at both ends, used as a connector.
9. An internally threaded piece which holds a bicycle spoke in place on the rim.

   “Turn the nipples on to the bicycle spokes only one turn, for each spoke on the new wheel all the way around until they are all snug, then check alignment.”

   “These were first constructed by heading the spokes, threading them through a steel felloe or rim and inserting them into screwed nipples which were in their turn screwed into the flanges of the hub.”

10. (humorous)A pointing stick.

verb

1. (transitive)To fit (a baby's bottle, etc.) with a nipple.
2. (transitive)To give one's nipple to (a baby) to allow breastfeeding.