The Collaborative International Dictionary of English v.0.48:

Opportunism \Op`por*tun"ism\, n. [Cf. F. opportunisme.]
   The art or practice of taking advantage of opportunities or
   circumstances, or of seeking immediate advantage with little
   regard for ultimate consequences. [Recent]
   [1913 Webster]

WordNet (r) 3.0 (2006):

opportunism
    n 1: taking advantage of opportunities without regard for the
         consequences for others [syn: opportunism, self-
         interest, self-seeking, expedience]