massing

The gradual massing of cars on the highway signaled the start of rush hour.

用法提示：此句用名词“massing”作主语，表示“逐渐聚集”的行为，与形容词“gradual”搭配。

We watched the massing of students in front of the library during exam week.

用法提示：此句用名词“massing”作“watched”的宾语，表示“学生聚集”的过程。

Because of the massing of clouds, we decided to postpone the picnic.

用法提示：此句用名词“massing”作介词“because of”的宾语，表示“云层聚集成团”的现象。