An orchestral piece at the beginning of an opera, play, etc. ‘the overture to Mozart’s ‘Don Giovanni’; Overture and Incidental Music for ‘A Midsummer Night’s Dream’’
An independent orchestral composition in one movement. ‘Tchaikovsky’s ‘1812 Overture’’
Origin
Late Middle English (in the sense ‘aperture’) : from Old French, from Latin apertura ‘aperture’.