adjective. Impossible to penetrate or enter.

adjective. Impossible to understand; incomprehensible.

adjective. Impervious to sentiment or argument.

Incapable of being penetrated; not penetrable, in any sense of that word.

Specifically, in physics, having the property of preventing any other substance from occupying the same place at the same time.

adjective. Incapable of being penetrated or pierced; not admitting the passage of other bodies; not to be entered; impervious.

adjective. Having the property of preventing any other substance from occupying the same space at the same time.

adjective. Inaccessible, as to knowledge, reason, sympathy, etc.; unimpressible; not to be moved by arguments or motives.

adjective. Not penetrable.

adjective. Incomprehensible; inscrutable.

adjective. not admitting of penetration or passage into or through

adjective. permitting little if any light to pass through because of denseness of matter

adjective. impossible to understand

"Announcing his response to a formal consultation, Cable outlined plans for greater diversity on boards – including requiring boards to contain two people who had never had seats in boardrooms before – and to make remuneration reports, which he described as "impenetrable", easier to understand."

penetrable  

dense  incomprehensible  thick  uncomprehensible  

dense  featureless  icy  impassable  impassive  

Greek to one  ambiguous  arcane  beyond reach  beyond understanding