How many letters does the top answer for “having two horns; two-horned; crescentlike.” have?

The most common answer is bicorn (6 letters).

Crossword clue: having two horns; two-horned; crescentlike.

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

bicorn 6 letters web-def

a cocked hat with the brim turned up to form two points

bicorned 8 letters web-def

a cocked hat with the brim turned up to form two points

bicornous 9 letters web-def

Having two horns; two-horned; crescentlike.