Abacus(redirected from Abbacus)
Also found in: Dictionary, Thesaurus, Encyclopedia, Wikipedia.
An instrument allowing one to quickly add and subtract numbers. Generally, an abacus is composed of a rectangular frame in which horizontal rods are partially covered with beads. The beads may be moved one way or the other to make calculations. It was invented in China in the 2nd century CE and is considered the earliest calculator.