Just a casual, everyday word for an umbrella. It’s the kind of shortening Brits love, and it pops up everywhere from school runs to train platforms when the weather’s doing its wet thing. Not posh, not super street, just friendly chat. If someone says grab your brolly, they’re saving you a soaking, not starting a fashion moment.
"Chuck a brolly in your tote, mate, it’s spitting again and the bus stop’s a wind tunnel. I’m not getting drenched for a ten-minute ride."