Definition: Antibiotic: A medication that inhibits bacterial growth by blocking the production of essential enzymes necessary for their growth, typically in order to prevent infection. Definition: Antibiotics are drugs that inhibit the growth of bacteria and other microorganisms that cause infections, such as strep throat or MRSA (molecularly targeted resistance). They work by disrupting the cell walls of bacteria to stop them from multiplying. This prevents the bacteria from causing harm to human cells and tissue through transmission in the body.