impromptuim‧promp‧tu /ɪmˈprɒmptjuː $ ɪmˈprɑːmptuː/ adjective 
The band gave an impromptu concert.—impromptu adverb
WORD ORIGINimpromptu
Origin:
1600-1700 French, Latin in promptu ‘in readiness’EXAMPLES FROM OTHER DICTIONARIES
- an impromptu performance
- Jem's impromptu speech met with thunderous applause.
- We finished the day with an impromptu game of football in a nearby field.
- But if friends descended, would you be ready to rustle up an impromptu supper?
- But in the final hour he did deliver the goods, taking impromptu questions from the audience.
- From that point, the forum became an impromptu tribute to Jim Maier.
- He had failed because of a lack of talent for impromptu speaking, considered essential for the task he was contemplating.
- I could then have pretended to notice him for the first time and have engaged him in conversation in an impromptu manner.
- Schwarm disputed the witness' story last week in an impromptu press conference outside court.
- The drunken revel of the Roman leaders has the right air of impromptu festivity.
- The remarks of both Clintons were, at least in part, impromptu.
Longman Language Activatornot planned
· As a surprise, we decided to make an unplanned visit to my mother's.· Very few burglaries are completely unplanned.· Unplanned pregnancies in the US each year are estimated at 3 million.
something that is spontaneous is done because you suddenly feel you want to do it, not because you have arranged to do it or been asked to do it: · The crowd gave a spontaneous cheer when the news was announced.· The invitation was completely spontaneous.· an act of spontaneous generosity
done or happening without any planning or preparation: · We finished the day with an impromptu game of football in a nearby field.· Jem's impromptu speech met with thunderous applause.
something that is not well thought out has not been planned carefully enough and therefore is unlikely to work well: · Reagan's plan was a bold one, but it was not well thought out.· If your business proposal is not very well thought out, you will find it difficult to get financial backing.
not planned or organized in advance: · You never know when you might have to have an ad hoc meeting with a client.· Historical records have often been kept in an ad hoc way, so that our information is not complete.on an ad hoc basis (=when you need to do it, not in a planned way): · Most companies have some people working for them on an ad hoc basis.
COLLOCATIONS FROM THE ENTRY The band gave an impromptu concert.
done or said without any preparation or planningimpromptu speech/party/meeting etc The band gave an impromptu concert. The band gave an impromptu concert.—impromptu adverb