roll (something) over something
phrasal verb with roll verb uk/rəʊl/ us/roʊl/
滚动，拖动（鼠标）
If you roll over something on a computer screen, you move the mouse over an active place so that you can see information that is hidden under it.
If you roll your mouse over a word, its definition will appear. 如果你把鼠标拖动到一个词上，这个词的定义就会显示出来。