In the US “sleet” is the term for a winter precipitation that occurs when snow falls through a layer of warm air and melts into water droplets, then re-freezes into ice pellets as it passes through colder air closer to the ground. In many other areas that were part of the British empire that precipitation is called “ice pellets” and “sleet” instead refers to a mix of snow and rain. In the US that’s called a “wintry mix.”
That’s just 2 English speaking countries, what about the others? Your title sounds like every English speaking country has a different meaning for the word ‘sleet’.
I guess in Zimbabwean English (spoken by more than 5 million people) doesn’t mean neither, as it doesn’t snow there. Do Canadians use the American or European meaning? This TIL raises more questions than it answers.
We use the British meaning. Yanks went their own way on this one.