impenetrable

About 1.37 uses per million words.

Meaning

1. adjective Not penetrable.

   The fortress is impenetrable, so it cannot be taken.

2. adjective Opaque; obscure; not translucent or transparent.
3. adjective Incomprehensible; fathomless; inscrutable.

   Business jargon makes this document impenetrable—I can’t understand it.

4. noun A person not openly given to friendship. (clarification of this definition is needed)

Similar words

uncomprehensible incomprehensible heavy dense thick impassable insuperable insurmountable inaccessible unfathomable

Often followed by

to darkness barrier and mystery wall as forests forest

Word family

impenetrably