σκυθρωπάζω
From LSJ
τοῖσι ἐμφανέσι τὰ μὴ γινωσκόμενα τεκμαιρόμενος → judge of the unknown by the known
English (LSJ)
A look angry or sullen, be of a sad countenance, Ar. Lys.7, Pl.756; ὡς οὐδὲν ἦσθα πλὴν σκυθρωπάζειν μόνον Amphis 13, cf. Antiph.218.3, PCair.Zen.481.30 (iii B.C.): aor. 1, ἐσκυθρώπασαν ἀκούσαντες X.Cyr.6.2.21; σφόδρα πάνυ σκυθρωπάσας Aeschin.2.36, cf. Thphr.Char.14.7: pf. ἐσκυθρωπακέναι Pl.Alc.2.138a; ἐσκυθρωπακώς D.45.68. 2 to be of a sad colour, Philostr.Im.1.28.