ک ث بk-th-b
(ن) كَثَبَ يَكْثُبُ كَثْبًاkathaba yakthubu kathban: to gather, to heap up.
كَثِيْبkathīb pl. كُثْبَانkuthbān: a sand dune. «مَهِيْلmahīl» means flowing, sliding down. Only once in the Quran, in the fate of the mountains on the Day of Resurrection: ﴿وَكَانَتِ الْجِبَالُ كَثِيْبًا مَّهِيْلًا﴾ (Al-Muzzammil 73:14).