τὸ σκυθρωπόν

From LSJ

τοῦ δὲ πολέμου οἱ καιροὶ οὐ μενετοί → in war, opportunities won't wait | the chances of war will not wait (Thucydides 1.142.2)

Source

Dutch (Woordenboekgrieks.nl)

slecht humeur, chagrijn, somberheid