countervail vs counterbalance

countervail is not a noun while counterbalance is a noun.

Word	Noun	Adjective	Verb	Adverb
countervail	No	No	Yes	No
counterbalance	Yes	No	Yes	No

As verbs, countervail and counterbalance are synonyms defined as:

countervail and counterbalance: oppose and mitigate the effects of by contrary actions

Other synonyms of countervail include counteract, neutralize.

countervail (noun)	counterbalance (noun)
	a weight that balances another weight
	a compensating equivalent
	equality of distribution

countervail (verb)	counterbalance (verb)
oppose and mitigate the effects of by contrary actions	oppose and mitigate the effects of by contrary actions
compensate for or counterbalance	contrast with equal weight or force
	adjust for