counterbalance

American Heritage® Dictionary of the English Language, Fourth Edition

1. n. A force or influence equally counteracting another.
2. n. A weight that acts to balance another; a counterpoise or counterweight.
3. v. To act as a counteracting force, influence, or weight to; counterpoise.
4. v. To oppose with an equal force; offset.

Century Dictionary and Cyclopedia

1. To weigh against with an equal weight; act against with equal power or effect; countervail; serve as a counterpoise to; offset; make up for.
2. n. Equal weight, power, or influence acting in opposition to anything.
3. n. In mech., a weight used to balance the vibrating parts of machinery upon their axis, so as to cause them to turn freely and to require little power to set them in motion; also, a weight by which a lever acted upon by an intermitting force is returned to its position, as in the case of the beam of a single-acting steam-engine; a counterpoise.
4. n. In elevators, a weight suspended on a rope which is attached to the car and passes over a pulley at the top of the elevator-shaft. The weight is usually heavier than the car, so as to allow for the average load.

Wiktionary

1. n. literally A weight that is put in opposition to an equal weight so it keeps that in balance.
2. n. figuratively A force or influence that balances, checks or limits an opposite one.
3. v. To apply weight in order to balance an opposing one.
4. v. To apply force in order to balance an opposite one.
5. v. figuratively To match or equal in effect, but acting in opposition

GNU Webster's 1913

1. v. To oppose with an equal weight or power; to counteract the power or effect of; to countervail; to equiponderate; to balance.
2. n. A mass of metal in one side of a driving wheel or fly wheel, to balance the weight of a crank pin, etc., on the opposite side of the wheel.
3. n. A counterpoise to balance the weight of anything, as of a drawbridge or a scale beam.

WordNet 3.0

1. n. equality of distribution
2. n. a compensating equivalent
3. n. a weight that balances another weight
4. v. adjust for
5. v. contrast with equal weight or force
6. v. oppose and mitigate the effects of by contrary actions