Snow would have made the road impassible in winter.

The Manichaeans were therefore, by reason of their dualism, arch-enemies no less of Christian art than of relics and cross-worship; the Monophysites were equally so by reason of their belief that the divine nature in Christ entirely absorbed and sublated the human; they shaded off into the party of the aphthartodoketes, who held that his human body was incorruptible and made of ethereal fire, and that his divine nature was impassible.

The main road to Enniskillen was virtually impassible in winter conditions and was a major concern.

The display was removed, the rain continued to fall, the traffic queues got longer and the ground became almost impassible.

impassible barrier, the Red Sea.