undermine vs countermine

undermine is not a noun while countermine is a noun.

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

As verbs, undermine and countermine are synonyms defined as:

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

undermine (noun)	countermine (noun)
	(military) a tunnel dug to defeat similar activities by the enemy

undermine (verb)	countermine (verb)
hollow out as if making a cave or opening	destroy enemy mines with one's own mines
destroy property or hinder normal operations	destroy property or hinder normal operations