Definition of bacillus in English:



  • 1A rod-shaped bacterium.

    • ‘The victim carried an enormous number of bacilli shaped with the typical ‘short rounded ends.’’
    • ‘One is a microscopic rod-shaped bacterium called bacillus anthracis, easy to grow in the lab but fragile and easily killed in the open.’
    • ‘At far right, Methanobacterium thermoautotrophicum, an elongate bacillus form.’
    1. 1.1A disease-causing bacterium.
      • ‘The man, who is unidentified as yet, does not have anthrax - the bacillus is on his person, but he's not infected, and with proper treatment, he should be fine.’
      • ‘When infectious people cough, sneeze, talk or spit, they propel TB germs, known as bacilli, into the air.’
      • ‘The book ends with the haunting observation that although the plague bacillus can go into hiding for years and years, it never dies or disappears for good.’
      • ‘Currently a third of the world's population carry the bacillus, albeit in a dormant form.’
      • ‘The isolation of the tuberculosis bacillus in 1882 by Robert Koch, who later became professor of hygiene and director of the Institute for Infectious Diseases in Berlin, was a scientific breakthrough.’


All bacteria belonging to the genus "Bacillus" are called bacilli, but not all bacteria called bacilli belong to the genus "Bacillus"


Late 19th century: from late Latin, diminutive of Latin baculus stick.