To weigh against with an equal weight; act against with equal power or effect; countervail; serve as a counterpoise to; offset; make up for.n. Equal weight, power, or influence acting in opposition to anything.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.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.