bacillus

noun

ba·​cil·​lus bə-ˈsi-ləs How to pronounce bacillus (audio)
plural bacilli bə-ˈsi-ˌlī How to pronounce bacillus (audio)
 also  -lē
1
: any of a genus (Bacillus) of rod-shaped gram-positive usually aerobic bacteria producing endospores and including many saprophytes and some parasites (such as B. anthracis of anthrax)
broadly : a straight rod-shaped bacterium
2
: bacterium
especially : a disease-producing bacterium

Examples of bacillus in a Sentence

Recent Examples on the Web Gut Guru Gummies contain up to 2 billion CFU of bacillus coagulans because good bacteria is key for a balanced gut. Amber Smith, Discover Magazine, 29 Oct. 2022 Key ingredients: Glyceryl glucoside, hydrolyzed yeast extract, bacillus ferment, polyglucuronic acid Size: 0.67 Fl. Iman Balagam, harpersbazaar.com, 6 May 2023 Recent analyses of global epidemiological data by several teams in the United States and in Israel found that in places with higher rates of bacillus Calmette-Guérin (BCG) tuberculosis vaccination, the spread of COVID-19 is slower and pandemic death rates are lower. Quanta Magazine, 14 Sep. 2020 The bacillus Calmette-Guérin vaccine against tuberculosis—or simply BCG—is the oldest vaccine in the world that is still currently in use. Viviane Callier, Scientific American, 19 Jan. 2023 To assist with muscle growth and recovery, use ingredients like tart cherry, turmeric extract, and 2 billion CFU probiotics (bacillus coagulans) after your workout. Amber Smith, Discover Magazine, 16 Nov. 2022 The peritonitis was the result of the undiagnosed gonorrhea that also led to pericarditis, pleurisy, arthritis in her hips and feet, and vulnerability to the tuberculosis bacillus. Frances Wilson, The New York Review of Books, 2 Feb. 2023 Scientists have found plague bacillus in a Neolithic tomb in Sweden, and earlier this year it was identified in a Bronze Age grave in Somerset. National Geographic, 19 July 2022 Mingheria, as Pamuk conceives it, is an impossible Eden, into which the bacillus of history must enter. James Wood, The New Yorker, 24 Oct. 2022 See More

These examples are programmatically compiled from various online sources to illustrate current usage of the word 'bacillus.' Any opinions expressed in the examples do not represent those of Merriam-Webster or its editors. Send us feedback about these examples.

Word History

Etymology

New Latin, from Medieval Latin, small staff, rod, diminutive of Latin baculus staff, alteration of baculum

First Known Use

1868, in the meaning defined at sense 1

Time Traveler
The first known use of bacillus was in 1868

Dictionary Entries Near bacillus

Cite this Entry

“Bacillus.” Merriam-Webster.com Dictionary, Merriam-Webster, https://www.merriam-webster.com/dictionary/bacillus. Accessed 28 Feb. 2024.

Kids Definition

bacillus

noun
ba·​cil·​lus bə-ˈsil-əs How to pronounce bacillus (audio)
plural bacilli -ˈsil-ˌī How to pronounce bacillus (audio)
 also  -ˈsil-ē
: any of numerous straight rod-shaped bacteria that require oxygen for growth
also : a disease-producing bacterium

Medical Definition

bacillus

noun
ba·​cil·​lus bə-ˈsil-əs How to pronounce bacillus (audio)
plural bacilli
-ˌī also -ē
1
a
capitalized : a genus of rod-shaped gram-positive endospore-producing usually aerobic bacteria of the family Bacillaceae that include many saprophytes and some parasites (as B. anthracis of anthrax)
b
: any bacterium of the genus Bacillus
broadly : a straight rod-shaped bacterium
2
: bacterium
especially : a disease-producing bacterium

More from Merriam-Webster on bacillus

Love words? Need even more definitions?

Subscribe to America's largest dictionary and get thousands more definitions and advanced search—ad free!