(1):

(n.) A weight, power, or agency, acting against or balancing another

(2):

(v. t.) To oppose with an equal weight or power; to counteract the power or effect of; to countervail; to equiponderate; to balance.

(3):

(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

(4):

(n.) A counterpoise to balance the weight of anything, as of a drawbridge or a scale beam.