unfathomable
US /ʌnˈfæð.ə.mə.bəl/
UK /ʌnˈfæð.ə.mə.bəl/
1.
incapable of being fully explored or understood
:
•
The depths of the ocean are still largely unfathomable.
•
His decision to leave was unfathomable to his family.
incapable of being fully explored or understood