[Latin bacillus, diminutive of baculum, rod or stick.]
A bacillus (plural bacilli) is a rod-shaped bacterium, often causing disease. Taking its meaning directly from its Latin source, something bacilliform is rod-shaped. However, compounds in medicine usually refer to the presence of disease-causing bacilli, as in bacillaemia (US bacillemia) (in the blood), or bacilluria (in the urine), in both cases as a result of infection; the adjective bacillary refers particularly to an infection caused by bacilli. See also bacterio-.