Lewis & Short

Pīcēnum, i, n. [acc. to Fest. from picus: Picena regio in quā est Asculum, dicta, quod, Sabini cum Asculum proficiscerentur, in vexillo eorum picus consederit, Paul. ex Fest. p. 212 Müll.], a district in the eastern part of Italy which produced fruits and oil of excellent quality, the territory of the mod. Ancona, Varr. R. R. 1, 50, 2; Mel. 2, 4, 6; Plin. 3, 13, 18, § 109; Cic. Att. 8, 8, 1; Caes. B. C. 1, 12; Liv. 27, 43 al.
Hence,

  1. A. Pīcens, entis, adj., of or belonging to Picenum, Picene: ager, Cic. Sen. 4, 11: populus, Liv. 10, 10 fin.: M. Acilius Palicanus, Picens, Quint. 4, 2, 2: panes, Macr. S. 2, 9.
    In plur. subst.: Pīcentes, ium, m., the inhabitants of Picenum, the Picenes, Cic. Sull. 8, 25.
    Gen.: Picentium, Varr. R. R. 1, 2; Plin. 3, 13, 18, § 110: Picentum, Sil. 10, 313.
    Sing.: Picens, Juv. 4, 65.
  2. B. Pī-cēnus, a, um, adj., Picene (only of things; whereas Picens is used both of persons and things): ager, Cic. Brut. 14, 57; Liv. 21, 62; Sall. C. 27, 1: vitis, Plin. 14, 3, 4, § 37: poma, Hor. S. 2, 3, 272: olivae, Plin. 15, 3, 4, § 16; cf. Mart. 5, 78, 20; 11, 52, 11; 13, 36, 1: mala, Juv. 11, 74 al.
  3. C. Pīcentīnus, a, um, adj., lit., of or belonging to the Picentes, Picentian, Picene (very rare): Ceres, Mart. 13, 47, 1.