preventer

This term is primarily used in technical, industrial, or medical contexts to describe a specific mechanism, agent, or person whose sole function is to stop an undesirable event. It carries a functional, utilitarian tone and is less common in everyday conversation than the verb "prevent" or the noun "prevention."

In chemical or biological contexts, it often refers to a stabilizer or inhibitor. When referring to a person, it describes someone acting in a protective or restrictive capacity, though this usage is rarer than the technical application.