The Collaborative International Dictionary of English v.0.48:

Outweigh \Out*weigh"\, v. t.
   To exceed in weight or value.
   [1913 Webster]

WordNet (r) 3.0 (2006):

outweigh
    v 1: be heavier than
    2: weigh more heavily; "these considerations outweigh our
       wishes" [syn: preponderate, outweigh, overbalance,
       outbalance]

Moby Thesaurus II by Grady Ward, 1.0:

41 Moby Thesaurus words for "outweigh":
   atone for, balance, best, better, cap, compensate for,
   counterbalance, counterpoise, countervail, exceed, excel,
   go one better, improve on, make up, make up for, offset,
   outbalance, outpoise, overbalance, overbear, overcome, overpass,
   overpoise, override, overtop, overweigh, overweight, perfect,
   predominate, preponderate, prevail, prevail over, redeem, set off,
   surpass, tip the scales, top, tower above, tower over, transcend,
   trump