A medicine which preserves or defends against disease; a preventive. / (US, specifically) A prophylactic condom. / (figuratively) Any device or mechanism intended to prevent harmful consequences.

Serving to prevent or protect against an undesired effect, especially disease or pregnancy

plural of prophylactic

Preventively.

prophylactic; preventative

plural of prophylactic rule

(law) A judge-made rule that overprotects a constitutional right in order to safeguard that right or facilitate detection of violations of it.