sneeze

American Heritage® Dictionary of the English Language, Fourth Edition

1. v. To expel air forcibly from the mouth and nose in an explosive, spasmodic involuntary action resulting chiefly from irritation of the nasal mucous membrane.
2. n. An instance or the sound of sneezing.
3. sneeze at Informal To treat as unimportant: These deficits are nothing to sneeze at.

Century Dictionary and Cyclopedia

1. To emit air from the nose and mouth audibly and violently by an involuntary convulsive action, as occasioned by irritation of the lining membrane of the nose or by stimulation of the retina by a brigbt light. In sneezing the glottis remains open. while the passage out through the mouth is partially obstructed by the approximation of the tongue to the roof of the mouth. See sneezing.
2. To utter with or like a sneeze.
3. n. The act of one who sneezes, or the sound made by sneezing; sudden and violent ejection of air through the nose and mouth with an audible sound.
4. n. Snuff. Also snish.

Wiktionary

1. v. To expel air as a reflex induced by an irritation in the nose.
2. v. To expel air as if the nose were irritated.
3. n. An act of sneezing.

GNU Webster's 1913

1. v. 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.
2. n. A sudden and violent ejection of air with an audible sound, chiefly through the nose.

WordNet 3.0

1. n. a symptom consisting of the involuntary expulsion of air from the nose
2. v. exhale spasmodically, as when an irritant entered one's nose