en_tn/jer/48/28.md

cliff

a steep side of a mountain

the mouth of a hole in the rocks

This refers to an opening in the rocks, such as the entrance to a cave.

arrogance, haughtiness, pride, self-glory, conceit in his heart

glory, conceit in his heart** - All of these words have similar meanings. They are used together to emphasize the extreme pride of the people of Moab.