To laugh your head off, usually at something so stupidly funny you can barely stand up. It’s that proper wheezing, clutching-your-stomach, sliding-off-the-sofa kind of laugh where you look like you’ve lost all bone structure. Often used as fall about laughing. Honestly, it’s the gold standard of British losing it.
"He tried to flip the burger and launched it into Auntie Pat’s Prosecco. We were falling about laughing while he stood there like a melted traffic cone"