Legionnaires' bacillus
noun
Le·gion·naires' bacillus
| \ ˌlē-jə-ˈna(ə)rz-, -ˈne(ə)rz-
\
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Medical Definition of Legionnaires' bacillus
: a bacterium of the genus Legionella (L. pneumophila) that causes Legionnaires' disease