[ buh-sil-uhs ]
/ bəˈsɪl əs /
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See synonyms for: bacillus / bacilli on Thesaurus.com

noun, plural ba·cil·li [buh-sil-ahy]. /bəˈsɪl aɪ/.
any rod-shaped or cylindrical bacterium of the genus Bacillus, comprising spore-producing bacteria.
(formerly) any bacterium.
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Origin of bacillus

1880–85; <Late Latin, variant of Latin bacillum (diminutive of baculum) staff, walking stick
Dictionary.com Unabridged Based on the Random House Unabridged Dictionary, © Random House, Inc. 2022

How to use bacillus in a sentence

British Dictionary definitions for bacillus

/ (bəˈsɪləs) /

noun plural -cilli (-ˈsɪlaɪ)
any rod-shaped bacterium, such as a clostridium bacteriumCompare coccus (def. 2), spirillum (def. 1)
any of various rodlike spore-producing bacteria constituting the family Bacillaceae, esp of the genus Bacillus

Word Origin for bacillus

C19: from Latin: a small staff, from baculum walking stick
Collins English Dictionary - Complete & Unabridged 2012 Digital Edition © William Collins Sons & Co. Ltd. 1979, 1986 © HarperCollins Publishers 1998, 2000, 2003, 2005, 2006, 2007, 2009, 2012

Medical definitions for bacillus (1 of 2)

[ bə-sĭləs ]

n. pl. ba•cil•li (-sĭlī′)
Any of various rod-shaped, usually gram-positive aerobic bacteria of the genus Bacillus that often occur in chains and include Bacillus anthracis, the causative agent of anthrax.
Any of various bacteria, especially a rod-shaped bacterium.

Medical definitions for bacillus (2 of 2)


A genus of rod-shaped gram-positive bacteria capable of producing endospores.
The American Heritage® Stedman's Medical Dictionary Copyright © 2002, 2001, 1995 by Houghton Mifflin Company. Published by Houghton Mifflin Company.

Scientific definitions for bacillus

[ bə-sĭləs ]

Plural bacilli (bə-sĭlī′)
Any of various pathogenic bacteria, especially one that is rod-shaped.
The American Heritage® Science Dictionary Copyright © 2011. Published by Houghton Mifflin Harcourt Publishing Company. All rights reserved.