Preventive

1. n. That which prevents, hinders, or obstructs; that which intercepts access; in medicine, something to prevent disease; a prophylactic.
2. a. Going before; preceding.
3. a. Tending to defeat or hinder; obviating; preventing the access of; as, a medicine preventive of disease.

The word meanings were obtained from OPTED(The Online Plain Text English Dictionary), which is based on “The Project Gutenberg Etext of Webster’s Unabridged Dictionary” which is in turn based on the 1913 US Webster’s Unabridged Dictionary (See Project Gutenburg), as a text file.