Impromptu means done without being planned or rehearsed. It describes something that is spontaneous, unplanned, or improvised.
Here are some examples of how the word is used:
* "The band gave an impromptu performance at the street festival."
* "We had an impromptu picnic in the park."
* "The comedian's jokes were completely impromptu."
Let me know if you have any other words you'd like to know the meaning of!