Counterbalance

[Sarah]

To oppose with an equal weight or power; to counteract thepower or effect of; to countervail; to equiponderate; to balance.The remaining air was not able to counterbalance the mercurialcylinder. Boyle.The cstudy of mind is necessary to counterbalance and correct theinfluence of the study of nature. Sir W. Hamilton.

[Britney]

A weight that balances another weight.