- Dense - Impervious - Incapable of being penetrated or pierced; not
admitting the passage of other bodies; not to be entered; impervious;
as, an impenetrable shield. - Having the property of preventing any other substance
from occupying the same space at the same time. - Inaccessible, as to knowledge, reason, sympathy,
etc.; unimpressible; not to be moved by arguments or motives; as, an
impenetrable mind, or heart.