Lewis & Short

Volsĭnĭi (Vulsĭnĭi), ōrum, m., a town in Etruria, now Bolsena, Plin. 2, 52, 53, § 139; Liv. 10, 37, 1; 27, 23, 3; Juv. 3, 191.
Hence,

  1. A. Volsĭnĭus, a, um, adj., of or belonging to Volsinii: foci, Prop. 4 (5), 2, 4.
  2. B. Volsĭnĭensis (Vuls-), e, adj., of or belonging to Volsinii, Volsinian: ager, Liv. 5, 32, 4: provincia, id. 5, 32, 4, § 2: lacus, a lake lying south of the town, now Lago di Bolsena, Col. 8, 16, 2; Plin. 36, 22, 49, § 168.
    Plur. subst.: Volsĭnĭen-ses (Vuls-), ĭum, m., the inhabitants of Volsinii, Volsinians, Plin. 3, 5, 8, § 52; Liv. 5, 31 sq.; 7, 3 al.