底そこ知しれぬ

expression, noun-modifying (irregular)

bottomless; unfathomable; immeasurable

Prenominal expression describing something so deep or vast that its limits cannot be perceived. Often used figuratively for emotions, potential, or darkness.

• 彼かれの目めには底そこ知しれぬ悲かなしみが浮うかんでいた。

  An unfathomable sadness showed in his eyes.

• 底そこ知しれぬ闇やみが洞どう窟くつの奥おくに広ひろがっていた。

  Bottomless darkness stretched deep inside the cave.