Pneumocystis
noun
Pneu·mo·cys·tis
| \ ˌn(y)ü-mə-ˈsis-təs
\
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Medical Definition of Pneumocystis
1
: a genus of ascomycetous fungi that were formerly classified as protozoans and include one (P. carinii synonym P. jiroveci) causing pneumonia especially in immunocompromised individuals