ha

from The American Heritage® Dictionary of the English Language, 5th Edition.

• abbreviation hectare
• abbreviation Latin hoc anno (this year)
• abbreviation hour angle
• interjection Used to express surprise, wonder, triumph, puzzlement, or pique.

from The Century Dictionary.

• An exclamation denoting surprise, wonder, joy, or other sudden emotion, as suspicion, and also interrogation. Repeated, ha! ha! it expresses either intensified surprise, etc., or laughter.
• An involuntary sound marking hesitation in speech, uttered slowly and obscurely, and otherwise represented by er or ur.
• noun Same as ha-ha, haw-haw.
• noun A contraction of have.
• An abbreviation of hectare.
• A dialectal variant of he.
• To make the sound ha, expressing hesitation.
• noun An expression of wonder, surprise, or admiration.
• noun An expression of hesitancy in speech.
• noun A Scotch form of hall.

from the GNU version of the Collaborative International Dictionary of English.

• interjection An exclamation denoting surprise, joy, or grief. Both as uttered and as written, it expresses a great variety of emotions, determined by the tone or the context. When repeated, ha, ha, it is an expression of laughter, satisfaction, or triumph, sometimes of derisive laughter; or sometimes it is equivalent to “Well, it is so.”

from Wiktionary, Creative Commons Attribution/Share-Alike License.

• noun hectare
• verb archaic Alternate spelling of a4
• interjection A representation of laughter.
• interjection An exclamation of triumph or discovery.

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

• noun (astronomy) the angular distance of a celestial point measured westward along the celestial equator from the zenith crossing; the right ascension for an observer at a particular location and time of day