decadrachm, deka-Numism.|ˈdɛkədræm| [f.Gr. δεκάδραχµος of the value of ten drachmæ, f. δέκα ten + δραχµή drachma.] An ancient Greek silver coin of the value of 10 drachmas. 1856Sat.Rev. II. 735/1 Pre-eminent amongst them was a decadrachm of Syracuse.