(September 2014). A general sales agent (GSA) is a sales representative for an airline in a specific country or region. Typically, the GSA is responsible for selling all products of the airline in its region which includes flight tickets and cargo space. A GSA will typically sell the product of more than one airline.
Definition of standing wave. : a single-frequency mode of vibration of a body or physical system in which the amplitude varies from place to place, is constantly zero at fixed points, and has maxima at other points.
Definition 1: A crest is a point on the wave where the displacement of the medium is at a maximum. A point on the wave is a trough if the displacement of the medium at that point is at a minimum.