Source : Webster's Revised Unabridged Dictionary (1913)

Signature \Sig"na*ture\, n. [F. (cf. It. signatura, segnatura,
   Sp. & LL. signatura), from L. signare, signatum. See {Sign},
   v. t.]
   1. A sign, stamp, or mark impressed, as by a seal.

            The brain, being well furnished with various traces,
            signatures, and images.               --I. Watts.

            The natural and indelible signature of God, which
            human souls . . . are supposed to be stamped with.
                                                  --Bentley.

   2. Especially, the name of any person, written with his own
      hand, employed to signify that the writing which precedes
      accords with his wishes or intentions; a sign manual; an
      autograph.

   3. (Physiol.) An outward mark by which internal
      characteristics were supposed to be indicated.

            Some plants bear a very evident signature of their
            nature and use.                       --Dr. H. More.

   4. (Old Med.) A resemblance between the external characters
      of a disease and those of some physical agent, for
      instance, that existing between the red skin of scarlet
      fever and a red cloth; -- supposed to indicate this agent
      in the treatment of the disease.

   5. (Mus.) The designation of the key (when not C major, or
      its relative, A minor) by means of one or more sharps or
      flats at the beginning of the staff, immediately after the
      clef, affecting all notes of the same letter throughout
      the piece or movement. Each minor key has the same
      signature as its relative major.

   6. (Print.)
      (a) A letter or figure placed at the bottom of the first
          page of each sheet of a book or pamphlet, as a
          direction to the binder in arranging and folding the
          sheets.
      (b) The printed sheet so marked, or the form from which it
          is printed; as, to reprint one or more signatures.

   Note: Star signatures (as A*, 1*) are the same characters,
         with the addition of asterisks, used on the first pages
         of offcuts, as in 12mo sheets.

   7. (Pharm.) That part of a prescription which contains the
      directions to the patient. It is usually prefaced by S or
      Sig. (an abbreviation for the Latin signa, imperative of
      signare to sign or mark).

Signature \Sig"na*ture\, v. t.
   To mark with, or as with, a signature or signatures.

Source : WordNet®

signature
     n 1: your name written in your own handwriting
     2: a distinguishing style; "this room needs a woman's touch"
        [syn: {touch}]
     3: a melody used to identify a performer or a dance band or
        radio/tv program [syn: {signature tune}, {theme song}]
     4: the sharps or flats that follow the clef and indicate the
        key [syn: {key signature}]
     5: a sheet with several pages printed on it; it folds to page
        size and is bound with other signatures to form a book

Source : Free On-Line Dictionary of Computing

signature
     
        1. A set of function symbols with {arities}.
     
        2.  (Or sig) A few lines of information about the
        sender of an {electronic mail} message or {news} {posting}.
        Most {Unix} mail and news software will {automagically} append
        a signature from a file called .signature in the user's {home
        directory} to outgoing mail and news.
     
        A signature should give your real name and your {e-mail
        address} since, though these appear in the {headers} of your
        messages, they may be {munged} by intervening software.  It is
        currently (1994) hip to include the {URL} of your {home page}
        on the {World-Wide Web} in your sig.
     
        The composition of one's sig can be quite an art form,
        including an {ASCII} logo or one's choice of witty sayings
        (see {sig quote}, {fool file}).  However, large sigs are a
        waste of {bandwidth}, and it has been observed that the size
        of one's sig block is usually inversely proportional to one's
        prestige on the net.
     
        See also {doubled sig}, {sig virus}.
     
        2.  A concept very similar to {abstract base
        classes} except that they have their own {hierarchy} and can
        be applied to compiled {classes}.  Signatures provide a means
        of separating {subtyping} and {inheritance}.  They are
        implemented in {C++} as patches to {GCC} 2.5.2 by Gerald
        Baumgartner .
     
        {(ftp://ftp.cs.purdue.edu/pub/gb/)}.
     
        (2001-01-05)