1. (a.) Going before; preceding.

2. (a.) Tending to defeat or hinder; obviating; preventing the access of; as, a medicine preventive of disease.

3. (n.) That which prevents, hinders, or obstructs; that which intercepts access; in medicine, something to prevent disease; a prophylactic.

aegis antacid anticipative anticipatory antidote arm guard backstop barrier block buffer bulwark bumper contraceptive copyright counteractant counteractive counteragent counterirritant countermeasure covering crash helmet curb cushion custodial dashboard defensive deterrent deterring discouraging dodger ethnocentric exceptional excluding exclusive exclusory face mask fender finger guard foot guard forbidding forestalling fostering fuse goggles governor guard guardian guarding guardrail hampering hand guard handrail hard hat helmet hindering hindrance immunizing impediment impeding inadmissible inhibiting inhibition inhibitive inhibitory inoculant inoculum insular insulation interdictive interdictory interlock knee guard knuckle guard laminated glass life preserver lifeline lightning conductor lightning rod mask mudguard narrow neutralizer nose guard nullifier obstacle obstruction offset pad padding palladium parental parochial patent pilot precautionary preclusive prescriptive preventative prevention prohibiting prohibitive prohibitory prophylactic proscriptive protecting protection protective protective clothing protective umbrella remedy repressive restraining restrictive safeguard safeguarding safety safety glass safety plug safety rail safety shoes safety switch safety valve screen screening seat belt seclusive segregative select selective separative serum sheltering shield shielding shin guard snobbish sun helmet suppressive tutelary umbrella vaccine vigilant watchful windscreen windshield xenophobic