undermine vs weaken

undermine and weaken both are verbs.

Word	Noun	Adjective	Verb	Adverb
undermine	No	No	Yes	No
weaken	No	No	Yes	No

As verbs, undermine and weaken are synonyms defined as:

Other synonyms of undermine include counteract, countermine, sabotage, subvert.

undermine (verb)	weaken (verb)
hollow out as if making a cave or opening	become weaker
destroy property or hinder normal operations	lessen the strength of
	reduce the level or intensity or size or scope of
	lessen in force or effect
	destroy property or hinder normal operations