πετρώδης
From LSJ
Τὸ νικᾶν αὐτὸν αὑτὸν πασῶν νικῶν πρώτη τε καὶ ἀρίστη. Τὸ δὲ ἡττᾶσθαι αὐτὸν ὑφ' ἑαυτοῦ πάντων αἴσχιστόν τε ἅμα καὶ κάκιστον. → Τo conquer yourself is the first and best victory of all, while to be conquered by yourself is of all the most shameful as well as evil
English (LSJ)
ες,
A like rock or stone, rocky, stony, π. κατῶρυξ, of a grave, S.Ant.774, cf. Porph.Antr.9; of ground, Hp.Aër.1; γεηρὰ καὶ πετρώδη καὶ ἄγρια Pl.R.612a; ἐν τοῖς τραχέσι καὶ πετρώδεσι Arist.HA549b14; τὸ π. BMus.Inscr.3.407.8 (Priene); ἄνθρωποι π. καὶ δενδρώδεις Heraclit.Incred.23; π. κεφαλή Philum.Ven.15.4.