a wave in which the direction of displacement is the same as the direction of propagation, as a sound wave.
Compare transverse wave.
Origin of longitudinal wave
First recorded in 1930–35
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A wave that oscillates back and forth on an axis that is the same as the axis along which the wave propagates. Sound waves are longitudinal waves, since the air molecules are displaced forward and backward on the same axis along which the sound travels. Compare transverse wave. See more at wave.
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