counteract vs countercheck

counteract is not a noun while countercheck is a noun.

Word	Noun	Adjective	Verb	Adverb
counteract	No	No	Yes	No
countercheck	Yes	No	Yes	No

As verbs, counteract and countercheck are synonyms defined as:

counteract (noun)	countercheck (noun)
	something that checks the correctness of a previous check
	a check that restrains another check

counteract (verb)	countercheck (verb)
act in opposition to	check a second time
destroy property or hinder normal operations	oppose or check by a counteraction
oppose or check by a counteraction
oppose and mitigate the effects of by contrary actions