Here are some other terms that are sometimes used:
* Extemporaneous speech: This is a speech that is delivered with limited preparation, often using notes or an outline.
* Off-the-cuff speech: This is similar to an impromptu speech, but it may involve some pre-planning.
* Unscripted speech: This is a speech that is not written out in advance.
It's important to note that while an impromptu speech is delivered without preparation, it doesn't mean it's completely unplanned. The speaker may have some general ideas or talking points in mind.