a disturbance that travels through a fluid as a narrow region in which there is a large, abrupt change in pressure and related quantities, esp. one separating regions of subsonic and supersonic fluid flow such as is created by an object moving faster than sound or by an explosion, gaasi tugeval ning järsul kokkusurumisel tekkiv liikuv pind, milles keskkonna tihedus, rõhk ja osakeste kiirus muutuvad hüppeliselt (näit. plahvatuste puhul)