ETYM Cf. French opportuniste.
A person who places expediency above principle; SYN. self-seeker.

Someone who makes excessive profit (especially on goods in short supply).

1. Taking advantage of opportunities as they arise: as exploiting opportunities with little regard to principle or consequences
2. Feeding on whatever food is available
3. Being or caused by a usually harmless microorganism that can become pathogenic when the host's resistance is impaired