(ˈ)im, əm+ adjective
Etymology: Middle English impenetrabel, from Middle French impenetrable, from Latin impenetrabilis, from in- in- (I) + penetrabilis penetrable — more at penetrable
1.
a. : incapable of being penetrated or pierced : not admitting the passage of other bodies : not to be entered : impervious
an impenetrable shield
an impenetrable forest
an impenetrable barrier
b. : inaccessible to knowledge, reason, sympathy : not to be moved by logic or other method of persuasion : unimpressible
an impenetrable heart
an impenetrable stupidity
c. : incapable of being dealt with in a way that brings a usually warm, cordial, or unguarded response
an impenetrable reserve
an impenetrable gloom
2. : incapable of being comprehended : inscrutable , unfathomable
an impenetrable mystery
a child speaking in an impenetrable language of its own
3. : having the property of impenetrability
impenetrable matter
• im·penetrableness “+ noun
• im·penetrably “+ adverb