What is the term for the lowest part of a progressive trough of a wave?

The term for the lowest part of a progressive trough of a wave is indeed wave trough. In oceanography, understanding wave behavior is vital, and waves consist of crests and troughs. The crest is the highest point of the wave, while the trough, which is the focus here, represents the lowest point.

Wave troughs are important as they reflect the energy dynamics of ocean waves. The distance between successive troughs (or crests) contributes to the wavelength, while the vertical distance between the crest and trough helps define wave height. Both wave height and wavelength are critical in assessing the energy and speed of a wave. The correct identification of the trough is essential for comprehending how waves interact with the seafloor and how they impact coastal processes.