General term for a chemical agent (such as chlorine) or a physical agent (such as heat or ultraviolet rays) that has the ability to kill most or all microorganisms (whether or not pathogenic) on external or internal wounds, clothing, or hard surfaces. This term covers antibiotics and antiseptics (some of which may be taken internally) and disinfectants, sanitizers, and sterilants (none of which are taken internally). Also called germicidal.