]> Acoustic Gravity Wave A wave disturbance with restoring forces that include buoyancy and the elastic compressibility of the fluid medium. Scattering of sound or ultrasound in the direction of the source. Acoustic Backscattering In radar, a general term for the appearance, on a radar display, of the radio signal scattered or reflected from a target. The characteristics of a radar echo are determined by 1) the waveform, frequency, and power of the incident wave; 2) the range and velocity of the target with respect to the radar; and 3) the size, shape, and composition of the target.