Source : Webster's Revised Unabridged Dictionary (1913)

Laxative \Lax"a*tive\, a. [L. laxativus mitigating, assuaging:
   cf. F. laxatif. See {Lax}, a.]
   1. Having a tendency to loosen or relax. --Milton.

   2. (Med.) Having the effect of loosening or opening the
      intestines, and relieving from constipation; -- opposed to
      {astringent}. -- n. (Med.) A laxative medicine. See the
      Note under {Cathartic}.

Source : WordNet®

laxative
     adj : stimulating evacuation of feces [ant: {costive}]
     n : a mild cathartic