[jonlong]

Wiki says that curl is standard in North America, while rot is common in "the rest of the world, particularly in 20th century scientific literature". As a North American I can confirm that I was always taught curl and only saw rot in older books.

That said ∇× is what I've seen most commonly overall.

[dboreham]

Scotland we used curl. I never heard of rot. Although Maxwell was Scottish, the vector analysis notation was invented later.

[xanderlewis]

In England we also seem to use curl. I’ve similarly never heard of rot.

[defrost]

Ditto 1980's era Australian physics and engineering courses.

Throw in a right hand thumbs up for "direction" of curl (fingers indicate rotation, orthogonal thumb direction is orientation) and other results about paths having to have a zero rotation between places with opposing rotation, etc.

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[xigoi]

I’m from Czechia and we mostly use rot, sometimes ∇×.