This word is acceptable for play in the US & UK dictionaries that are being used in the following games:

• Lexulous
• Wordscraper
• Wordosaur

n. The amount that will fit into a hat

n. A large number (usually talking about goalscoring chances)

n. (often followed by `of') a large number or amount or extent

n. as many or as much as a hat will hold

"He was in a very good temper, however, for he had won what his companions called a hatful of money on the steeple-chase, and he stood to win on other races that were to come off that afternoon."

containerful   

hateful   

fistful    shovelful    pocketful    basketful    mind-bogglingly    mycelia    midden    lapful    juggle    not-so-subtle