Sleet is winter weather: rain that is half frozen, or a cold mix of rain and tiny ice, so what hits your coat is wet ice — not soft snow, and not the hard stones of hail. It makes pavements slippery and miserable. In everyday British English, sleet is the ordinary word for that icy rain. Americans use it too, though weather presenters there sometimes split hairs between sleet, freezing rain, and ice pellets; for ordinary talk, if wet ice is falling, people still say it is sleeting. It is a noun (“We had sleet all morning”) and a verb (“It sleeted overnight”). You cannot hold a piece of sleet the way you can hold a snowball; it is more a kind of falling weather than a thing in your hand. Taiwan almost never gets this, so you will meet the word in stories, news, and exams more than on the street.