countercheck vs counteract

countercheck is a noun but counteract is not a noun.

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

As verbs, countercheck and counteract are synonyms defined as:

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

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