The Collaborative International Dictionary of English v.0.48:

Party \Par"ty\ (p[aum]r"t[y^]), n.; pl. Parties
   (p[aum]r"t[i^]z). [F. parti and partie, fr. F. partir to
   part, divide, L. partire, partiri. See Part, v.]
   1. A part or portion. [Obs.] "The most party of the time."
      --Chaucer.
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   2. A number of persons united in opinion or action, as
      distinguished from, or opposed to, the rest of a community
      or association; esp., one of the parts into which a people
      is divided on questions of public policy.
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            Win the noble Brutus to our party.    --Shak.
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            The peace both parties want is like to last.
                                                  --Dryden.
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   3. A part of a larger body of company; a detachment;
      especially (Mil.), a small body of troops dispatched on
      special service.
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   4. A number of persons invited to a social entertainment; a
      select company; as, a dinner party; also, the
      entertainment itself; as, to give a party.
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   5. One concerned or interested in an affair; one who takes
      part with others; a participator; as, he was a party to
      the plot; a party to the contract.
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   6. The plaintiff or the defendant in a lawsuit, whether an
      individual, a firm, or corporation; a litigant.
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            The cause of both parties shall come before the
            judges.                               --Ex. xxii. 9.
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   7. Hence, any certain person who is regarded as being opposed
      or antagonistic to another.
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            If the jury found that the party slain was of
            English race, it had been adjudged felony. --Sir J.
                                                  Davies.
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   8. Cause; side; interest.
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            Have you nothing said
            Upon this Party 'gainst the Duke of Albany? --Shak.
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   9. A person; as, he is a queer party. [Now accounted a
      vulgarism.]
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   Note: "For several generations, our ancestors largely
         employed party for person; but this use of the word,
         when it appeared to be reviving, happened to strike,
         more particularly, the fancy of the vulgar; and the
         consequence has been, that the polite have chosen to
         leave it in their undisputed possession." --Fitzed.
         Hall.
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   Party jury (Law), a jury composed of different parties, as
      one which is half natives and half foreigners.

   Party man, a partisan. --Swift.

   Party spirit, a factious and unreasonable temper, not
      uncommonly shown by party men. --Whately.

   Party verdict, a joint verdict. --Shak.

   Party wall.
      (a) (Arch.) A wall built upon the dividing line between
          two adjoining properties, usually having half its
          thickness on each property.
      (b) (Law) A wall that separates adjoining houses, as in a
          block or row.
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