From Longman Dictionary of Contemporary Englishbe a hootbe a hootspokenFUNNY to be very funny or amusing → hoot
Examples from the Corpus
be a hoot• The movie has a script that is smartly funny, and Hugh Grant is a hoot!• I thought Judy's performance was a real hoot.• At the end of the day, there was the moms' soccer match, which was a hoot! 