i 1 m 3 p 3 e 1 n 1 e 1 t 1 r 1 a 1 b 3 i 1 l 1 i 1 t 1 i 1 e 1 s 1
17 letters · 23 points in Scrabble
Meaning
noun the quality of being impenetrable (by people or light or missiles etc.)
noun incomprehensibility by virtue of being too dense to understand