今天我们要学的单词是：impromptu。
这是一个名词，副词和形容词，作为形容词，表示即席的。
例如：你可以说："John and his team had to give an impromptu presentation on monthly sales projection because the president of the company unexpectedly stopped by their branch." （因为总裁没有按预期地前来察看他们的分公司，约翰和他的团队必须针对月销售项目作出即兴汇报总结。）