οὖσα

From LSJ

Μισῶ γε μέντοι χὤταν ἐν κακοῖσί τις ἁλοὺς ἔπειτα τοῦτο καλλύνειν θέλῃ → I hate it when someone is caught in the midst of their evil deeds and tries to gloss over them

Sophocles, Antigone, 495-496

French (Bailly abrégé)

ης;
fém. de ὤν, part. prés. de εἰμί.

Russian (Dvoretsky)

οὖσα: f к ὤν (part. praes. к εἰμί).