The Collaborative International Dictionary of English v.0.48:

affirmative action \affirmative action\ n.
   1. a policy of making active efforts to improve the
      employment or educational opportunities available to
      members of minority groups or women; -- achieved by
      employers or schools by using various techniques, but
      excluding the use of simple quotas or outright
      discrimination against white males.

   Note: affirmative action is required by law for certain
         employers in the United States.
         [PJC]

WordNet (r) 3.0 (2006):

affirmative action
    n 1: a policy designed to redress past discrimination against
         women and minority groups through measures to improve their
         economic and educational opportunities; "affirmative action
         has been extremely controversial and was challenged in 1978
         in the Bakke decision"