A compression wave is one that is considered to be a type of shock waves. A shock wave is one that moves fast. It moves more quickly than the speed of sound. This compression wave that squeezes together, possibly in the middle. Adjacent is one that is nearby. Therefore, the adjacent stream compressions are those shock waves that are located close to each other and move fast. Based on the speed of individual flows, this would determine their distance because for some waves.
There is an average distance between the same types of waves. Therefore, for the next wave compressions, the distance between these two types of waves that are taking place nearby is by one wavelength. A wavelength is a distance between two streams at the same two points.