What are the best answers for “making great mental demands; hard to comprehend or solve or believe”?

baffling, problematic, problematical.

How many letters does the top answer for “making great mental demands; hard to comprehend or solve or believe” have?

The most common answer is baffling (8 letters).

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

baffling 8 letters wn-def

making great mental demands; hard to comprehend or solve or believe

problematic 11 letters wn-def

making great mental demands; hard to comprehend or solve or believe

problematical 13 letters wn-def

making great mental demands; hard to comprehend or solve or believe