Im-pēn'e-tra-ble, a.
a. [Fr. impénétrable, Sp. impenetrable, It. impenetrabile, Lat. impenetrabilis, from prefix im, for in, not, and penetrabilis, penetrable.]
Sense 1. Incapable of being penetrated or pierced; not admitting the passage of other bodies; not to be entered; as, an impenetrable shield.
Highest woods impenetrable To star or sunlight. Milton.
Sense 2. Hence, inaccessible, as to knowledge, reason, sympathy, &c.; unimpressible; not to be moved by arguments or motives; as, an impenetrable mind or heart.
They will be credulous in all affairs of life, but impenetrable by a sermon of the gospel. Bp. Taylor.