The Collaborative International Dictionary of English v.0.48:

Nipple \Nip"ple\ (n[i^]p"p'l), n. [Formerly neble, a dim. of
   neb. See Neb, Nib.]
   1. (Anat.) The protuberance through which milk is drawn from
      the breast or mamma; the mammilla; a teat; a pap.
      [1913 Webster]

   2. The orifice at which any animal liquid, as the oil from an
      oil bag, is discharged. [R.] --Derham.
      [1913 Webster]

   3. Any small projection or article in which there is an
      orifice for discharging a fluid, or for other purposes;
      as, the nipple of a nursing bottle; the nipple of a
      percussion lock, or that part on which the cap is put and
      through which the fire passes to the charge.
      [1913 Webster]

   4. (Mech.) A pipe fitting, consisting of a short piece of
      pipe, usually provided with a screw thread at each end,
      for connecting two other fittings.
      [1913 Webster]

   Solder nipple, a short pipe, usually of brass, one end of
      which is tapered and adapted for attachment to the end of
      a lead pipe by soldering.
      [1913 Webster]

WordNet (r) 3.0 (2006):

nipple
    n 1: the small projection of a mammary gland [syn: nipple,
         mammilla, mamilla, pap, teat, tit]
    2: a flexible cap on a baby's feeding bottle or pacifier

Moby Thesaurus II by Grady Ward, 1.0:

64 Moby Thesaurus words for "nipple":
   adjutage, bag, boobs, bosom, breast, breasts, brisket, bust,
   catheter, chest, crop, drainpipe, dug, efflux tube, fire hose,
   flue pipe, funnel, garden hose, gas pipe, hose, hosepipe, knockers,
   mama, mamelon, mamelonation, mammary gland, mammilla, mammillation,
   nenes, organ pipe, pap, papilla, pigeon breast, pipe, pipeline,
   pipette, piping, reed, reed pipe, siamese, siamese connection,
   siphon, snorkel, soil pipe, standpipe, steam pipe, stem, straw,
   tap, teat, thorax, tit, tits, titties, titty, tube, tubing,
   tubulation, tubule, tubulet, tubulure, udder, waste pipe,
   water pipe



The Free On-line Dictionary of Computing (30 December 2018):

nipple

   Trackpoint