- any of several spherical bacteria of the genus Staphylococcus, occurring in pairs, tetrads, and irregular clusters, certain species of which, as S. aureus, can be pathogenic for humans.
- any spherical Gram-positive bacterium of the genus Staphylococcus, typically occurring in clusters and including many pathogenic species, causing boils, infection in wounds, and septicaemia: family Micrococcaceae
