A dense,white,fluffy,flat-based cloud with a multiple rounded top and a well-defined outline,usually formed by the ascent of thermally unstable air masses.

• 积云一种浓密、平底状的白色云块，有一个多重圆形的顶部和界线分明的轮廓，通常是由不稳定的热气团上升形成的。