The Collaborative International Dictionary of English v.0.48:

Proboscis \Pro*bos"cis\, n.; pl. Proboscides. [L. fr. Gr. ?; ?
   before + ? to feed, graze.]
   1. (Zool.) A hollow organ or tube attached to the head, or
      connected with the mouth, of various animals, and
      generally used in taking food or drink; a snout; a trunk.
      [1913 Webster]

   Note: The proboscis of an elephant is a flexible muscular
         elongation of the nose. The proboscis of insects is
         usually a chitinous tube formed by the modified
         maxill[ae], or by the labium. See Illusts. of
         Hemiptera and Lepidoptera.
         [1913 Webster]

   2. (Zool.) By extension, applied to various tubelike mouth
      organs of the lower animals that can be everted or
      protruded.
      [1913 Webster]

   Note: The proboscis of annelids and of mollusks is usually a
         portion of the pharynx that can be everted or
         protruded. That of nemerteans is a special long
         internal organ, not connected with the mouth, and not
         used in feeding, but capable of being protruded from a
         pore in the head. See Illust. in Appendix.
         [1913 Webster]

   3. The nose. [Jocose]
      [1913 Webster]

   Proboscis monkey. (Zool.) See Kahau.
      [1913 Webster]

WordNet (r) 3.0 (2006):

proboscis
    n 1: the human nose (especially when it is large)
    2: a long flexible snout as of an elephant [syn: proboscis,
       trunk]

Moby Thesaurus II by Grady Ward, 1.0:

23 Moby Thesaurus words for "proboscis":
   antlia, beak, beezer, bill, bugle, conk, muffle, muzzle, nares,
   neb, nib, nose, nostrils, nozzle, olfactory organ, pecker,
   rhinarium, rostrum, schnozzle, smeller, snoot, snout, trunk



The Devil's Dictionary (1881-1906):

PROBOSCIS, n.  The rudimentary organ of an elephant which serves him
in place of the knife-and-fork that Evolution has as yet denied him.
For purposes of humor it is popularly called a trunk.
    Asked how he knew that an elephant was going on a journey, the
illustrious Jo. Miller cast a reproachful look upon his tormentor, and
answered, absently:  "When it is ajar," and threw himself from a high
promontory into the sea.  Thus perished in his pride the most famous
humorist of antiquity, leaving to mankind a heritage of woe!  No
successor worthy of the title has appeared, though Mr. Edward Bok, of
_The Ladies' Home Journal_, is much respected for the purity and
sweetness of his personal character.