descriptive, expression · happening in a sudden, abrupt, or agitated manner, often describing a sharp change in emotion or countenance

他听了这些侮辱性的言语，不禁勃然大怒。

descriptive · with energy, intensity, or vitality; describing something that is flourishing or rising up strongly

这股改革的浪潮在全国范围内勃然兴起。