travelling wave

/T R AE1 V AH0 L IH0 NG W EY0 V/
noun
  1. 1

    A wave that is not bounded by a given space, but can propagate freely

  2. 2

    A wave in which the vibration is in the direction of propagation; a longitudinal wave

Source: https://en.wiktionary.org/wiki/travelling%20wave