τὸ σκυθρωπόν

From LSJ

τίς δ' οἶδεν εἰ τὸ ζῆν μέν ἐστι κατθανεῖν, τὸ κατθανεῖν δὲ ζῆν κάτω νομίζεται → who knows if life is death, and if in the underworld death is considered life

Source

Dutch (Woordenboekgrieks.nl)

slecht humeur, chagrijn, somberheid