What are the best answers for “incomprehensibility by virtue of being too dense to understand”?

impenetrability, impenetrableness.

How many letters does the top answer for “incomprehensibility by virtue of being too dense to understand” have?

The most common answer is impenetrability (15 letters).

2 answers found in Letterora's clue database (Wikidata facts, Open Trivia DB, WordNet and Webster definitions — all licensed sources).

impenetrability 15 letters wn-def

incomprehensibility by virtue of being too dense to understand

impenetrableness 16 letters wn-def

incomprehensibility by virtue of being too dense to understand