undulate vs undulation

undulate is not a noun while undulation is a noun.

Word	Noun	Adjective	Verb	Adverb
undulate	No	Yes	Yes	No
undulation	Yes	No	No	No

undulate (noun)	undulation (noun)
	(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

undulate (adjective)	undulation (adjective)
having a wavy margin and rippled surface

undulate (verb)	undulation (verb)
increase and decrease in volume or pitch, as if in waves
move in a wavy pattern or with a rising and falling motion
stir up (water) so as to form ripples
occur in soft rounded shapes