1. not virulent; lacking the ability to cause disease or harm; not poisonous or toxic
Usage: commonly used in microbiology and medicine

Examples

• The avirulent strain of the virus was used safely in the laboratory.
• Scientists developed an avirulent vaccine that could protect without causing illness.
• The bacteria became avirulent after repeated culturing in the lab.
• An avirulent form of the pathogen was discovered in the patient's sample.
• The researchers confirmed the mutant was avirulent and posed no health risk.