How many letters does the top answer for “not precisely determined or established; not fixed or known in advance” have?

The most common answer is indeterminate (13 letters).

Crossword clue: not precisely determined or established; not fixed or known in advance

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

indeterminate 13 letters wn-def

not precisely determined or established; not fixed or known in advance

undetermined 12 letters wn-def

not precisely determined or established; not fixed or known in advance