Source : Webster's Revised Unabridged Dictionary (1913)

A \A\ ([.a]), prep. [Abbreviated form of an (AS. on). See {On}.]
   1. In; on; at; by. [Obs.] ``A God's name.'' ``Torn a
      pieces.'' ``Stand a tiptoe.'' ``A Sundays'' --Shak. ``Wit
      that men have now a days.'' --Chaucer. ``Set them a
      work.'' --Robynson (More's Utopia).

   2. In process of; in the act of; into; to; -- used with
      verbal substantives in -ing which begin with a consonant.
      This is a shortened form of the preposition an (which was
      used before the vowel sound); as in a hunting, a building,
      a begging. ``Jacob, when he was a dying'' --Heb. xi. 21.
      ``We'll a birding together.'' `` It was a doing.'' --Shak.
      ``He burst out a laughing.'' --Macaulay.

   Note: The hyphen may be used to connect a with the verbal
         substantive (as, a-hunting, a-building) or the words
         may be written separately. This form of expression is
         now for the most part obsolete, the a being omitted and
         the verbal substantive treated as a participle.

A \A\ ([.a] emph. [=a]).
   1. [Shortened form of an. AS. [=a]n one. See {One}.] An
      adjective, commonly called the indefinite article, and
      signifying one or any, but less emphatically. ``At a
      birth''; ``In a word''; ``At a blow''. --Shak.

   Note: It is placed before nouns of the singular number
         denoting an individual object, or a quality
         individualized, before collective nouns, and also
         before plural nouns when the adjective few or the
         phrase great many or good many is interposed; as, a
         dog, a house, a man; a color; a sweetness; a hundred, a
         fleet, a regiment; a few persons, a great many days. It
         is used for an, for the sake of euphony, before words
         beginning with a consonant sound [for exception of
         certain words beginning with h, see {An}]; as, a table,
         a woman, a year, a unit, a eulogy, a ewe, a oneness,
         such a one, etc. Formally an was used both before
         vowels and consonants.

   2. [Originally the preposition a (an, on).] In each; to or
      for each; as, ``twenty leagues a day'', ``a hundred pounds
      a year'', ``a dollar a yard'', etc.

A \A\ [From AS. of off, from. See {Of}.]
   Of. [Obs.] ``The name of John a Gaunt.'' ``What time a day is
   it ?'' --Shak. ``It's six a clock.'' --B. Jonson.

A \A\
   A barbarous corruption of have, of he, and sometimes of it
   and of they. ``So would I a done'' ``A brushes his hat.''
   --Shak.

A \A\
   An expletive, void of sense, to fill up the meter

         A merry heart goes all the day, Your sad tires in a
         mile-a.                                  --Shak.

A \A\ (named [=a] in the English, and most commonly ["a] in
   other languages).
   The first letter of the English and of many other alphabets.
   The capital A of the alphabets of Middle and Western Europe,
   as also the small letter (a), besides the forms in Italic,
   black letter, etc., are all descended from the old Latin A,
   which was borrowed from the Greek {Alpha}, of the same form;
   and this was made from the first letter (?) of the
   Ph[oe]nician alphabet, the equivalent of the Hebrew Aleph,
   and itself from the Egyptian origin. The Aleph was a
   consonant letter, with a guttural breath sound that was not
   an element of Greek articulation; and the Greeks took it to
   represent their vowel Alpha with the ["a] sound, the
   Ph[oe]nician alphabet having no vowel symbols. This letter,
   in English, is used for several different vowel sounds. See
   Guide to pronunciation, [sect][sect] 43-74. The regular long
   a, as in fate, etc., is a comparatively modern sound, and has
   taken the place of what, till about the early part of the
   17th century, was a sound of the quality of ["a] (as in far).

   2. (Mus.) The name of the sixth tone in the model major scale
      (that in C), or the first tone of the minor scale, which
      is named after it the scale in A minor. The second string
      of the violin is tuned to the A in the treble staff. -- A
      sharp (A[sharp]) is the name of a musical tone
      intermediate between A and B. -- A flat (A[flat]) is the
      name of a tone intermediate between A and G.

   {A per se} (L. per se by itself), one pre["e]minent; a
      nonesuch. [Obs.]

            O fair Creseide, the flower and A per se Of Troy and
            Greece.                               --Chaucer.

Source : WordNet®

A
     n 1: the blood group whose red cells carry the A antigen [syn: {type
          A}, {group A}]
     2: a metric unit of length equal to one ten billionth of a
        meter (or 0.0001 micron); used to specify wavelengths of
        electromagnetic radiation [syn: {angstrom}, {angstrom unit}]
     3: any of several fat-soluble vitamins essential for normal
        vision; prevents night blindness or inflammation or
        dryness of the eyes [syn: {vitamin A}, {antiophthalmic
        factor}, {axerophthol}]
     4: one of the four nucleotides used in building DNA; all four
        nucleotides have a common phosphate group and a sugar
        (ribose) [syn: {deoxyadenosine monophosphate}]
     5: (biochemistry) purine base found in DNA and RNA; pairs with
        thymine in DNA and with uracil in RNA [syn: {adenine}]
     6: the basic unit of electric current adopted under the Systeme
        International d'Unites; "a typical household circuit
        carries 15 to 50 amps" [syn: {ampere}, {amp}]
     7: the 1st letter of the Roman alphabet

Source : Free On-Line Dictionary of Computing

A#
     
         /A sharp/ A separable component of Version 2 of the
        {AXIOM*} computer algebra system.  It provides a programming
        language with an {optimising compiler}, an {intermediate code}
        {interpreter}, and a library of data structures and
        mathematical {abstraction}s.  The compiler produces
        {stand-alone executable} programs, {object} libraries in
        {native} {operating system} formats, {portable} {bytecode}
        libraries, {C} and {Lisp} {source code}.
     
        The A# programming language has support for {object-oriented}
        and {functional programming} styles.  Both types and functions
        are {first class} values that can be manipulated with a range
        of flexible and composable {primitive}s and user programs.
        The A# language design places particular emphasis on
        compilation for efficient {machine code} and portability.
     
        Ports have been made to various 16, 32, and 64 bit
        architectures: {RS/6000}, {SPARC}, {DEC Alpha}, {i386},
        {i286}, {Motorola 680x0}, {S 370}; several {operating
        system}s: {Linux}, {AIX}, {SunOS}, {HP/UX}, {Next}, {Mach} and
        other {Unix} systems, {OS/2}, {DOS}, {Microsoft Windows},
        {VMS} and {CMS}; {C} compilers: {Xlc}, {gcc}, {Sun},
        {Borland}, {Metaware} and {MIPS} C.
     
        (1995-02-07)