Any of various rod-shaped, spore-forming aerobic bacteria in the genus Bacillus, some of which cause disease. / Any bacilliform (rod-shaped) bacterium.

(bacteriology) A variety of bacillus shaped like a comma, found in the intestines of patients suffering from cholera.

bacillus of the genus Lactobacillus

(now chiefly historical) The bacterium Mycobacterium tuberculosis, which causes tuberculosis.

The bacillus Salmonella enterica subsp. enterica, the cause of typhoid.

Corynebacterium diphtheriae, the pathogenic bacterium that causes diphtheria.