counterbalance

Short definition from Wiktionary

Noun

1. 1
   A weight that is put in opposition to an equal weight so it keeps that in balance.
2. 2
   A force or influence that balances, checks or limits an opposite one.

Verb

1. 1
   To apply weight in order to balance an opposing weight.
2. 2
   To match or equal in effect when applying opposing force.