The Collaborative International Dictionary of English v.0.48:

Piece \Piece\, n. [OE. pece, F. pi[`e]ce, LL. pecia, petia,
   petium, probably of Celtic origin; cf. W. peth a thing, a
   part, portion, a little, Armor. pez, Gael. & Ir. cuid part,
   share. Cf. Petty.]
   1. A fragment or part of anything separated from the whole,
      in any manner, as by cutting, splitting, breaking, or
      tearing; a part; a portion; as, a piece of sugar; to break
      in pieces.
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            Bring it out piece by piece.          --Ezek. xxiv.
                                                  6.
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   2. A definite portion or quantity, as of goods or work; as, a
      piece of broadcloth; a piece of wall paper.
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   3. Any one thing conceived of as apart from other things of
      the same kind; an individual article; a distinct single
      effort of a series; a definite performance; especially:
      (a) A literary or artistic composition; as, a piece of
          poetry, music, or statuary.
      (b) A musket, gun, or cannon; as, a battery of six pieces;
          a following piece.
      (c) A coin; as, a sixpenny piece; -- formerly applied
          specifically to an English gold coin worth 22
          shillings.
      (d) A fact; an item; as, a piece of news; a piece of
          knowledge.
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   4. An individual; -- applied to a person as being of a
      certain nature or quality; often, but not always, used
      slightingly or in contempt. "If I had not been a piece of
      a logician before I came to him." --Sir P. Sidney.
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            Thy mother was a piece of virtue.     --Shak.
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            His own spirit is as unsettled a piece as there is
            in all the world.                     --Coleridge.
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   5. (Chess) One of the superior men, distinguished from a
      pawn.
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   6. A castle; a fortified building. [Obs.] --Spenser.
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   Of a piece, of the same sort, as if taken from the same
      whole; like; -- sometimes followed by with. --Dryden.

   Piece of eight, the Spanish piaster, formerly divided into
      eight reals.

   To give a piece of one's mind to, to speak plainly,
      bluntly, or severely to (another). --Thackeray.

   Piece broker, one who buys shreds and remnants of cloth to
      sell again.

   Piece goods, goods usually sold by pieces or fixed
      portions, as shirtings, calicoes, sheetings, and the like.
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WordNet (r) 3.0 (2006):

piece of eight
    n 1: an old silver Spanish coin; worth 8 reales