done without preparation or planning无准备的；即兴的；即席的 synonym improvised- an impromptu speech即兴讲演
- They often held impromptu meetings in their house.他们经常在家里即兴聚会。
Oxford Collocations DictionaryImpromptu is used with these nouns: See full entry Word Originmid 17th cent. (as an adverb): from French, from Latin in promptu ‘in readiness’, from promptus ‘brought to light’, also ‘prepared, ready’, past participle of promere ‘to produce’, from pro- ‘out, forth’ + emere ‘take’.