Abacus \Ab"a*cus\ ([a^]b"[.a]*k[u^]s), n.; E. pl. {Abacuses}; L.
   pl. {Abaci} (-s[imac]). [L. abacus, abax, Gr. 'a`bax]
   1. A table or tray strewn with sand, anciently used for
      drawing, calculating, etc. [Obs.]
      
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   2. A calculating table or frame; an instrument for performing
      arithmetical calculations by balls sliding on wires, or
      counters in grooves, the lowest line representing units,
      the second line, tens, etc. It is still employed in China.
      
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   3. (Arch.)
      (a) The uppermost member or division of the capital of a
          column, immediately under the architrave. See
          {Column}.
      (b) A tablet, panel, or compartment in ornamented or
          mosaic work.
          
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   4. A board, tray, or table, divided into perforated
      compartments, for holding cups, bottles, or the like; a
      kind of cupboard, buffet, or sideboard.
      
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   {Abacus harmonicus} (Mus.), an ancient diagram showing the
      structure and disposition of the keys of an instrument.
      --Crabb.
      
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