fall about laughing

To be consumed by uncontrollable laughter. Primarily heard in UK. We all fell about laughing when the professor accidentally swore during his lecture. My brother-in-law's wicked sense of humor has us falling about laughing every time we hang out with him. Once one actor falls about laughing, it's only a matter of time until their scene partners join them.

fall about with laughter

To be consumed by uncontrollable laughter. Primarily heard in UK. We all fell about with laughter when the professor accidentally swore during his lecture. My brother-in-law's wicked sense of humor has us falling about with laughter every time we hang out with him. Once one actor falls about with laughter, it's only a matter of time until their scene partners join them.

fall about (laughing/with laughter)

(British English, informal) laugh a lot: When he watches Charlie Chaplin films, he falls about laughing. I don’t find them funny at all!