The Collaborative International Dictionary of English v.0.48:

Counterbalance \Coun`ter*bal"ance\ (-b?l"ans), v. t. [imp. & p.
   p. Counterbalanced (-anst); p. pr. & vb. n.
   Counterbalancing.]
   To oppose with an equal weight or power; to counteract the
   power or effect of; to countervail; to equiponderate; to
   balance.
   [1913 Webster]

         The remaining air was not able to counterbalance the
         mercurial cylinder.                      --Boyle.
   [1913 Webster]

         The study of mind is necessary to counterbalance and
         correct the influence of the study of nature. --Sir W.
                                                  Hamilton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Counterbalance \Coun"ter*bal`ance\ (koun"t?r-b?l`ans), n.
   A weight, power, or agency, acting against or balancing
   another; as:
   (a) 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.
   (b) A counterpoise to balance the weight of anything, as of a
       drawbridge or a scale beam.
       [1913 Webster]

             Money is the counterbalance to all other things
             purchasable by it.                   --Locke.
       [1913 Webster] counter-balanced

WordNet (r) 3.0 (2006):

counterbalance
    n 1: a weight that balances another weight [syn:
         counterweight, counterbalance, counterpoise,
         balance, equalizer, equaliser]
    2: equality of distribution [syn: balance, equilibrium,
       equipoise, counterbalance]
    3: a compensating equivalent [syn: counterbalance, offset]
    v 1: adjust for; "engineers will work to correct the effects or
         air resistance" [syn: compensate, counterbalance,
         correct, make up, even out, even off, even up]
    2: contrast with equal weight or force [syn: oppose,
       counterbalance]
    3: oppose and mitigate the effects of by contrary actions; "This
       will counteract the foolish actions of my colleagues" [syn:
       counteract, countervail, neutralize, counterbalance]

Moby Thesaurus II by Grady Ward, 1.0:

133 Moby Thesaurus words for "counterbalance":
   accommodate, adjust, amend, annul, antipode, antipodes, antipole,
   antithesis, antonym, atone for, balance, ballast,
   be at cross-purposes, be heavy, be opposed to, bring to nothing,
   buffer, cancel, cancel out, carry weight, clash, come to nothing,
   compensate, conflict, conflict with, consideration, contra,
   contradict, contrapose, contrast with, contravene, controvert,
   converse, coordinate, correct, counter, counteract, counterblast,
   countercheck, countercurrent, counterforce, counterinfluence,
   counterpoint, counterpoise, counterpole, counterpose,
   counterpressure, counterterm, countervail, counterweigh,
   counterweight, counterwork, crosscurrent, equalize, equate,
   equipoise, equiponderate, equivalent, even, even up, firm, firm up,
   fit, foil, foul wind, freeze, frustrate, give-and-take,
   have weight, head wind, heft, hold, hold the scales, immobilize,
   integrate, invalidate, inverse, juxtapose in opposition, keep,
   level, lie heavy, make up, makeweight, nail down, negate,
   negativate, negative, neutralize, nullify, obverse, offset, oppose,
   opposite, opposite number, oppugn, outweigh, pin down,
   play at cross-purposes, poise, proportion, quid pro quo, rectify,
   redeem, retain, reverse, run counter to, set off, setoff,
   something of value, square, square up, stabilitate, stabilize,
   steady, stick, strike a balance, stultify, the contrary,
   the other side, thwart, tip the scales, tit for tat, transfix,
   undercurrent, undo, vis-a-vis, vitiate, void, weigh, weigh heavy,
   weigh in, weigh out, weight