roll(sth)oversth
—phrasal verbwithrollverbuk/rəʊl/us/roʊl/
If yourollover something on acomputerscreen, youmovethemouseover anactiveplaceso that you canseeinformationthat ishiddenunder it.
滚动，拖动（鼠标）
If yourollyourmouseover a word,itsdefinitionwillappear.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。