The most common and enduring British slang term for an umbrella is a "brolly." This colloquialism, which dates back to the late 19th century, is a classic example of British "clipping," where a long word is shortened and given a "y" or "ie" ending. While you will certainly hear "umbrella" used in formal contexts, "brolly" is the standard term in casual conversation, weather reports, and even retail advertising in 2026. You might also encounter the more vintage (and slightly humorous) term "gamp," named after the character Sarah Gamp in Charles Dickens' Martin Chuzzlewit, who was famous for carrying a large, messy umbrella. Another, albeit rarer, term is a "mush," though this is mostly confined to London's Cockney rhyming slang heritage. Given the UK's notoriously unpredictable rainfall, the phrase "Don't forget your brolly!" is one of the most frequently spoken sentences across the British Isles, reflecting a culture that is perpetually prepared for a sudden downpour regardless of the season or forecast.