(Lat. decimatio), a tithing; a selection of every tenth person by lot.

The term decimatio was applied by the Romans to a punishment inflicted on such soldiers as quitted their posts, or had been guilty of any crime. The names of the guilty were put into an urn or helmet; and as many having been drawn out as made the tenth part of the whole number, these were punished. The Romans had also the vicecinatio, and even centesimatio, when only the twentieth or the hundredth man suffered by lot.