arithmometer|ærɪθˈmɒmɪtə(r)| [a. F. arithmomètre, f. as arithmomancy + Gr. -µέτρον: see -meter.] An instrument for working out arithmetical problems. 1876in S. Kens. Sci.Catal.1879Thomson & Tait Nat.Phil. I. i. §401 Calculating Machines.. up to the Arithmometer of Thomas of Colmar [in 1862].