How many letters does the top answer for “the quantity that can be held in the mouth” have?

The most common answer is mouthful (8 letters).

Crossword clue: the quantity that can be held in the mouth

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

mouthful 8 letters wn-def

the quantity that can be held in the mouth

the quantity that can be held in a mug 60% similar → mugful

the quantity that can be held in the hand 60% similar → fistful, handful

the quantity that can be held in the lap 60% similar → lapful