1. spoke or performed without preparation; improvised
Usage: past tense of extemporise; British spelling

Examples

• She extemporised a speech when the main speaker failed to arrive.
• The musician extemporised a beautiful melody on the piano.
• He extemporised his presentation after forgetting his notes.
• The actor extemporised his lines when he forgot the script.
• The teacher extemporised a lesson plan when the projector broke.
• She extemporised a recipe using whatever ingredients were available.