A diplococcus (plural diplococci) is a round bacterium (a coccus) that typically occurs in the form of two joined cells. Examples of gram-negative diplococci are Neisseria sp., Moraxella catarrhalis, Acinetobacter, and Brucella. Examples of gram-positive diplococci would be and enterococcus.
The word diplococcus is derived from "diplo", meaning double, and "coccus", meaning berry (referring to its spherical, ovoid, and generally round shape).
In former times, a bacterial genus Diplococcus was recognized, but it is not used anymore.