φρουρεῖν
From LSJ
Ἐχθροὺς ἀμύνου μὴ ‘πὶ τῇ σαυτοῦ βλάβῃ → Ulciscere hostem, non tamen damno tuo → Die Feinde wehre ohne Schaden für dich ab
Greek > English (Woodhouse Verbs Reversed)
(see also φρουρέω): guard, protect, watch, be on the look out, keep watch