from The American Heritage® Dictionary of the English Language, 5th Edition.

  • noun A nonmotile, gram-positive bacterium (Streptococcus pneumoniae) that is the most common cause of bacterial pneumonia and is a cause of meningitis and other infectious diseases.

from The Century Dictionary.

  • noun A diplococcus which is regarded as the causative factor of acute croupous pneumonia. Also termed diplococcus pneumoniæ or Fraenkel's pneumococcus. See diplococcus.

from the GNU version of the Collaborative International Dictionary of English.

  • noun (Biol.) A form of micrococcus found in the sputum (and elsewhere) of persons suffering with pneumonia, and thought to be the cause of this disease.

from Wiktionary, Creative Commons Attribution/Share-Alike License.

  • noun A gram-positive bacterium, Streptococcus pneumoniae, that causes pneumonia and other infectious diseases

from WordNet 3.0 Copyright 2006 by Princeton University. All rights reserved.

  • noun bacterium causing pneumonia in mice and humans


from Wiktionary, Creative Commons Attribution/Share-Alike License

pneumo- + -coccus


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  • "Although many bacteria, viruses, and fungi can invade the lung, the single most common cause of pneumonia is the pneumococcus, a bacterium that can be either a primary or a secondary invader. (It causes approximately 95 percent of lobar pneumonias, involving one or more lobes, although a far lesser percentage of bronchopneumonias.) ... Under the microscope the pneumococcus looks like a typical streptococcus, a medium-size elliptical or round bacterium usually linked with others in a chain, although the pneumococcus usually is linked only to one other bacterium—and is sometimes called a diplococcus—like two pearls side by side. When exposed to sunlight it dies within ninety minutes, but it survives in moist sputum in a dark room for ten days. It can be found occasionally on dust particles."

    —John M. Barry, The Great Influenza (NY: Penguin Books, 2004), 153

    February 14, 2009