πευστέος

From LSJ

σιγᾶν ἄμεινον ἢ λαλεῖν ἃ μὴ πρέπει → it's better to keep silence than to say what's not appropriate (Menander)

Source

German (Pape)

[Seite 607] adj. verb. zu πεύθομαι, πυνθάνομαι, zu fragen, zu erforschen, Plat. u. A.