The Collaborative International Dictionary of English v.0.48:

Tradeoff \Trade"off\, Trade-off \Trade"-off\, n.
   1. the exchange of one thing (object, right, opportunity) for
      another of approximately equal value, so as to seal a
      bargain, or effect a compromise.
      [PJC]

   2. the giving up of one desired objective in order to attain
      another, when both cannot be achieved at the same time;
      as, the factory workers viewed the trade-off of air
      quality for jobs as a necessary evil.
      [PJC]

WordNet (r) 3.0 (2006):

trade-off
    n 1: an exchange that occurs as a compromise; "I faced a
         tradeoff between eating and buying my medicine" [syn:
         tradeoff, trade-off]