Adjective
Moving in the manner of undulations, or waves; resembling the motion of waves, which successively rise or swell rise or swell and fall; pertaining to a propagated alternating motion, similar to that of waves.
Source: Webster's dictionaryA standing wave (black) depicted as the sum of two propagating waves traveling in opposite directions (red and blue) Standing waves A standing wave is an undulatory motion that stays in one place. Source: Internet
Among Arago's many contributions to the support of the undulatory hypothesis, comes the experimentum crucis which he proposed to carry out for measuring directly the velocity of light in air and in water and glass. Source: Internet