unfathomable
US /ʌnˈfæð.ə.mə.bəl/
UK /ʌnˈfæð.ə.mə.bəl/

1.
insondável, incompreensível, profundo
incapable of being fully explored or understood
:
•
The depths of the ocean are still largely unfathomable.
As profundezas do oceano ainda são em grande parte insondáveis.
•
His decision to leave was unfathomable to his family.
Sua decisão de partir era incompreensível para sua família.