Lewis & Short

3. Pīso, ōnis, m.,

  1. I. a Roman surname in the gens Calpurnia; v. Calpurnius, Cic. Font. 13, 39; Juv. 5, 109.
    Hence,
  2. II. Pīsōnĭ-ānus, a, um, adj., of or belonging to a Piso, Pisonian: Pisoniana conjuratio, Suet. Ner. 36: Pisoniano vitio, cum loqui nesciret, tacere non potuit (with reference to Cic. Pis. 1, 1, where Cicero charges Piso with lack of eloquence), Hier. Ep. 69, 2.