impenetrable
US /ɪmˈpen.ə.trə.bəl/
UK /ɪmˈpen.ə.trə.bəl/
1.
impossible to pass through or enter
:
•
The fortress had an impenetrable defense system.
•
The dense jungle was almost impenetrable.
2.
impossible to understand; incomprehensible
:
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His handwriting was almost impenetrable.
•
The philosopher's theories were often impenetrable to the average person.