Webster's Revised Unabridged Dictionary · 1913

Obolus

Obolus , noun

[Latin, from Greek ({not transcribed})]

(a)
(GreekAntiquities) A small silver coin of Athens, the sixth part of a drachma, about three cents in value.
(b)
(GreekAntiquities) An ancient weight, the sixth part of a drachm.