undervalue vs underestimate

undervalue is not a noun while underestimate is a noun.

Word	Noun	Adjective	Verb	Adverb
undervalue	No	No	Yes	No
underestimate	Yes	No	Yes	No

As verbs, undervalue and underestimate are synonyms defined as:

undervalue (noun)	underestimate (noun)
	an estimation that is too low; an estimate that is less than the true or actual value

undervalue (verb)	underestimate (verb)
lose in value	make a deliberately low estimate
assign too low a value to	make too low an estimate of
esteem lightly	assign too low a value to