adjective. Too deep to be fathomed or measured.

adjective. Too obscure or complicated to be understood.

Incapable of being embraced or encompassed with the arms.

Having a depth so great that it cannot be fathomed; bottomless.

Not to be penetrated by thought or comprehended.

adjective. Incapable of being fathomed; immeasurable; that can not be sounded.

adjective. Incomprehensible.

adjective. Very deep (especially of water deeper than a lead line can measure); bottomless

adjective. unfathomable or incomprehensible

"It is indeed a fathomless mystery of theology, and even if I were theologian enough to deal with it directly, it would not be relevant to do so here."

unintelligible  

azure  bottomless  boundless  cloudless  depthless  

immeasurable  incomprehensible