ALLIA, a river of Italy, in the Sabine territory, which running down a very steep channel from the mountains of Crustuminum, mixes with the Tiber 40 miles from Rome; famous for the great slaughter of the Romans by the Gauls, under Brennus, when 40,000 Romans were killed or put to flight; hence Alliensis dies, an unlucky day, (Virgil, Ovid, Lucan.) Our ancestors, says Cicero, deemed the day of the fight of Allia more fatal than that of taking the city.