The Collaborative International Dictionary of English v.0.48:

Sneeze \Sneeze\, v. i. [imp. & p. p. Sneezed; p. pr. & vb. n.
   Sneezing.] [OE. snesen; of uncertain origin; cf. D. snuse
   to sniff, E. neese, and AS. fne['o]san.]
   To emit air, chiefly through the nose, audibly and violently,
   by a kind of involuntary convulsive force, occasioned by
   irritation of the inner membrane of the nose.
   [1913 Webster]

   Not to be sneezed at, not to be despised or contemned; not
      to be treated lightly. [Colloq.] "He had to do with old
      women who were not to be sneezed at." --Prof. Wilson.
      [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Sneeze \Sneeze\, n.
   A sudden and violent ejection of air with an audible sound,
   chiefly through the nose.
   [1913 Webster]

WordNet (r) 3.0 (2006):

sneeze
    n 1: a symptom consisting of the involuntary expulsion of air
         from the nose [syn: sneeze, sneezing, sternutation]
    v 1: exhale spasmodically, as when an irritant entered one's
         nose; "Pepper makes me sneeze"

Moby Thesaurus II by Grady Ward, 1.0:

100 Moby Thesaurus words for "sneeze":
   Aqua-Lung, artificial respiration, aspiration, assibilate,
   assibilation, asthmatic wheeze, blow, breath, breath of air,
   breathe, breathe hard, breathe in, breathe out, breathing,
   broken wind, buzz, cough, effervesce, effervescence, effervescing,
   exhalation, exhale, exhaust, expel, expiration, expire,
   exsufflation, fizz, fizzle, fizzling, frication,
   frictional rustling, gasp, gulp, hack, hiccup, hiss, hissing, huff,
   hush, hushing, inhalation, inhalator, inhale, inspiration, inspire,
   insufflation, iron lung, lisp, mouth-to-mouth resuscitation,
   oxygen mask, oxygen tent, pant, puff, respiration, respire,
   rhonchus, scuba, shush, shushing, sibilance, sibilate, sibilation,
   siffle, sigh, sigmatism, siss, sissing, sizz, sizzle, sizzling,
   sneer, sneeze at, sneezing, sniff, sniffle, snore, snoring, snort,
   snuff, snuffle, spit, splutter, sputter, squash, squelch, squish,
   sternutation, stertor, suspiration, swish, wheeze, whish, whistle,
   whistling, white noise, whiz, whoosh, wind, zip