1. An organism that may resort to parasitic activity, but does not absolutely rely on any host for completion of its life cycle. (wikipedia.org)
2. A parasite that does not live exclusively on a given host species. (entomology.montana.edu)
3. An organism that normally lives as a saprophyte but under certain conditions can live as a parasite. (ppath.cornell.edu)
4. An organism that lives independent of a host but may occasionally be parasitic under certain conditions. (biology-online.org)