impenetrable /ɪmˈpɛnətɹəbəl/adjective 3noun 1forms 1 adjective3 •Not penetrable.The fortress is impenetrable, so it cannot be taken. •Opaque; obscure; not translucent or transparent.When night falls, she cloaks the world in impenetrable darkness. — 1991 •(figurative) Incomprehensible; fathomless; inscrutable.Business jargon makes this document impenetrable—I can’t understand it. noun1 •A person not openly given to friendship. formsimpenetrables
