\Pre*serv"a*tive\, a. [Cf. F. pr['e]servatif.]
Having the power or quality of preserving; tending to
preserve, or to keep from injury, decay, etc.

\Pre*serv"a*tive\, n.
That which preserves, or has the power of preserving; a
presevative agent.
      To wear tablets as preservatives against the plague.
                                               --Bacon.