Noun | 1. | diplococcus - Gram-positive bacteria usually occurring in pairs bacteria, bacterium - (microbiology) single-celled or noncellular spherical or spiral or rod-shaped organisms lacking chlorophyll that reproduce by fission; important as pathogens and for biochemical properties; taxonomy is difficult; often considered to be plants genus Diplococcus - a genus of bacteria Diplococcus pneumoniae, pneumococcus - bacterium causing pneumonia in mice and humans |