undescendableadj.
Etymology: Previous versions of the OED give the stress as: undeˈscendable.
the world > movement > motion in a certain direction > downward motion > [adjective] > that cannot be descended into
1876 Ld. Tennyson i. i. 2 Steam'd upward from the undescendable Abysm.
This entry has not yet been fully updated (first published 1921; most recently modified version published online March 2020).