How many letters does the top answer for “the quality of not being doable” have?

The most common answer is infeasibility (13 letters).

Crossword clue: the quality of not being doable

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

infeasibility 13 letters wn-def

the quality of not being doable

unfeasibility 13 letters wn-def

the quality of not being doable

the quality of being doable 75% similar → feasibility, feasibleness

the quality of not being devout 60% similar → irreligion, irreligiousness

the quality of not being exchangeable 60% similar → inconvertibility

the quality of not being safe 60% similar → dangerousness

the quality of not being suitable 60% similar → unfitness

the quality of not being usable 60% similar → impracticability, impracticableness

the quality of being alien or not native 50% similar → curiousness, foreignness

the quality of being concrete (not abstract) 50% similar → concreteness