travelling wave vs undulation

travelling wave and undulation both are nouns.

Word	Noun	Adjective	Verb	Adverb
travelling wave	Yes	No	No	No
undulation	Yes	No	No	No

As nouns, undulation is a hypernym of travelling wave; that is, undulation is a word with a broader meaning than travelling wave:

travelling wave: a wave in which the medium moves in the direction of propagation of the wave
undulation: (physics) a movement up and down or back and forth

Other hypernyms of travelling wave include wave.

travelling wave (noun)	undulation (noun)
a wave in which the medium moves in the direction of propagation of the wave	(physics) a movement up and down or back and forth
	wavelike motion; a gentle rising and falling in the manner of waves
	an undulating curve