Incapable of suffering injury or detriment.

Incapable of suffering, or of sustaining injury: = impassible, adj. 1 2.

Of tried or proven strength or quality; (originally esp. of armour) of tested power of resistance. figurative and in extended use: impenetrable…

Incapable of being wounded; not liable to be physically hurt or damaged.

That cannot be wounded; invulnerable. Obsolete.

Of persons or lives: Fortified, protected, rendered invulnerable, etc., by a spell or charm.

(un-, prefix1 affix 1b.)

Not capable of being, or liable to be, exposed.

Not obnoxious; not exposed to; not offensive, inoffensive.

Used for impregnable, adj. n.

That cannot be wrecked.

(un-, prefix1 affix 1b.)

figurative. Wholly protected (from something injurious or distasteful); not susceptible or responsive (to something).