From Longman Dictionary of Contemporary Englishfall about phrasal verb British EnglishLAUGHto laugh a lot about something It was so funny everyone just fell about laughing. → fall→ See Verb table
Examples from the Corpus
fall about• When we heard the news, we just fell about!• When they saw what their father had done, they both fell about laughing.fell about laughing• He fell about laughing when his agent phoned him with this news. 