The Collaborative International Dictionary of English v.0.48:

Capital \Cap"i*tal\, a. [F. capital, L. capitalis capital (in
   senses 1 & 2), fr. caput head. See Chief, and cf.
   Capital, n.]
   1. Of or pertaining to the head. [Obs.]
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            Needs must the Serpent now his capital bruise
            Expect with mortal pain.              --Milton.
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   2. Having reference to, or involving, the forfeiture of the
      head or life; affecting life; punishable with death; as,
      capital trials; capital punishment.
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            Many crimes that are capital among us. --Swift.
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            To put to death a capital offender.   --Milton.
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   3. First in importance; chief; principal.
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            A capital article in religion         --Atterbury.
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            Whatever is capital and essential in Christianity.
                                                  --I. Taylor.
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   4. Chief, in a political sense, as being the seat of the
      general government of a state or nation; as, Washington
      and Paris are capital cities.
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   5. Of first rate quality; excellent; as, a capital speech or
      song. [Colloq.]
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   Capital letter [F, lettre capitale] (Print.), a leading or
      heading letter, used at the beginning of a sentence and as
      the first letter of certain words, distinguished, for the
      most part, both by different form and larger size, from
      the small (lower-case) letters, which form the greater
      part of common print or writing.

   Small capital letters have the form of capital letters and
      height of the body of the lower-case letters.

   Capital stock, money, property, or stock invested in any
      business, or the enterprise of any corporation or
      institution. --Abbott.

   Syn: Chief; leading; controlling; prominent.
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WordNet (r) 3.0 (2006):

capital stock
    n 1: the maximum number of shares authorized under the terms of
         a corporation's articles of incorporation [syn: authorized
         shares, authorized stock, capital stock]
    2: the book value of the outstanding shares of a corporation