Definitions of preventive:

• noun:   remedy that prevents or slows the course of an illness or disease
• noun:   an agent or device intended to prevent conception
• noun:   any obstruction that impedes or is burdensome
• adjective:   tending to prevent or hinder
• adjective:   preventing or contributing to the prevention of disease

  Example: "Preventive medicine"

• adjective:   tending to ward off