underestimate vs undervalue

underestimate is a noun but undervalue is not a noun.

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

As verbs, underestimate and undervalue are synonyms defined as:

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

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