What does abacus mean?
The definition of abacus
Ab”a*cus, n. E. pl. Abacuses ; L. pl. Abaci.
Etym: [L. abacus, abax, Gr.

1 A table or tray strewn with sand, anciently used for drawing, calculating, etc. [Obs.]
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.
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.

4 A board, tray, or table, divided into perforated compartments, for holding cups, bottles, or the like; a kind of cupboard, buffet, or sideboard. Abacus harmonicus (Mus.), an ancient diagram showing the structure and disposition of the keys of an instrument. Crabb.