ripple vs undulate

ripple is a noun but undulate is not a noun.

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

As verbs, ripple and undulate are synonyms defined as:

Other synonyms of ripple include cockle, riffle, ruffle.

ripple (noun)	undulate (noun)
a small wave on the surface of a liquid
(electronics) an oscillation of small amplitude imposed on top of a steady value

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

ripple (verb)	undulate (verb)
stir up (water) so as to form ripples	increase and decrease in volume or pitch, as if in waves
flow in an irregular current with a bubbling noise	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