στυγνητός

From LSJ

πάντα χωρεῖ καὶ οὐδὲν μένει καὶ δὶς ἐς τὸν αὐτὸν ποταμὸν οὐκ ἂν ἐμβαίης → all things move and nothing remains still, and you cannot step twice into the same stream

Source

English (Strong)

from a derivative of an obsolete apparently primary stugo (to hate); hated, i.e. odious: hateful.