…well anybody?
Sure. I even use that term when appropriate
Heavy rain.
edited to spoiler,
A hard rainstorm that comes down fast and often leads to flash flooding in low-lying areas. Leading to the name.
Yup. I’ve been known to use that phrase from time to time.
In a convienance store I frequent it’s a extra-extra large soda for the unbelievable price of $1.99. It’s looks like a gallon size cup. Very big.
( I also know it’s a rain flooded creek bed or ditch, with a fast flow)
Never heard it in Canada.
Being from Texas, it is commonly used there, but I’ve only met a few people outside of Texas that knew the meaning of the term.
Sure - it’s the little flat part that’s installed underneath the head of a gully bolt. 
One who washes a gully.
Luxury. We lived in a lake…
[/Yorkshire Accent]
Can’t say I would ever use it, but I know what it means. It’s a folksy way to say a mo-fo of a rainstorm.
Think of an avalanche only with water.
I think it is pretty well understood by any country person who lives in the kind of arid region where there are flash floods.
Almost anyone in the US over 40 should have known. Kids under 30, maybe not so likely.
I know the term; I’m pretty sure that I learned it from my mother. She grew up in a mid-sized town in Wisconsin, but both of her parents had grown up in rural areas, and she has a smattering of “farm terms” in her vocabulary as a result.
In Putin’s Russia, gully wash YOU!
We also used the phrase “gully whomper”
(born and raised in southern Indiana)
I think a “gully washer” is one of those medieval professions that became obsolete on the path towards modernity, in this case with the invention of the bidet. The position of royal gully washer, the Groom of the Stool, was much sought-after among courtiers due to its close proximity to the king.
I got it from Dad, who was 100 per cent Canadian.
mmm