nipple

Short definition from Wiktionary

Noun

1. 1
   The projection of a mammary gland from which, on female therian mammals, milk is secreted.
2. 2
   The nipple (definition 1) and the areola together.
3. 3
   A mechanical device through which liquids or gases can be passed in a regulated manner.
4. 4
   An artificial nipple (definition 1) used for bottle-feeding infants.
5. 5
   Any small physical protrusion, such as the lumps on the F and J keys on computer keyboards.
6. 6
   Any small physical protrusion on an automotive, a machine part or any other part that fits into a groove on another part.
7. 7
   A perforated segment that fits into part of the breech of a muzzle-loading gun, on which the percussion cap is fixed.
8. 8
   A short tube threaded at both ends, used as a connector.
9. 9
   An internally threaded piece which holds a bicycle spoke in place on the rim.
10. 10
    A pointing stick.

Verb

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