Means scarpering out sharpish, usually because you’ve legged it without paying or you don’t fancy the consequences. Classic for doing a taxi or restaurant bill, or bolting the moment someone’s about to kick off. It implies dodgy behaviour and a bit of panic, not a graceful exit. If you do a runner, you’re gone before anyone can say oi.
"Gary nicked the last sausage roll, the bouncer clocked him, and he did a runner out the kebab shop, leaving his mate to pay like a mug."