Source : Webster's Revised Unabridged Dictionary (1913)

Opportunist \Op`por*tun"ist\, n. [Cf. F. opportuniste.]
   One who advocates or practices opportunism. [Recent]

Source : WordNet®

opportunist
     n : a person who places expediency above principle [syn: {self-seeker}]

opportunist
     adj : taking immediate advantage, often unethically, of any
           circumstance of possible benefit [syn: {opportunistic},
            {timeserving}]