opportunistic
Pronunciation:
/ˌɑpəɹˌtuːˈnɪstɪk/adjective
Definitions
Taking advantage of situations that arise.
Example: The danger now isn't so much from the AIDS virus itself as from opportunistic infections.
Taking advantage of situations to advance one's own interests without regard for moral principles.
Example: You can't trust somebody that opportunistic: he'll stab you in the back the first chance he gets.