ἄῤῥεκτος

From LSJ

ἔξαψις σφοδρὰ μετὰ πολλῆς βίας πίπτουσα ἐπὶ γῆς → a violent flare-up falling on the ground with great force, thunder and lightning

Source

German (Pape)

[Seite 359] ungemacht, unvollendet, s. ἄρεκτος.