Wordnet 3.0
NOUN (1)
1. 
 a mild cathartic; 
ADJECTIVE (1)
1. 
 stimulating evacuation of feces; 
The Collaborative International Dictionary of English v.0.48:
Laxative \Lax"a*tive\, a. [L. laxativus mitigating, assuaging:
   cf. F. laxatif. See Lax, a.]
   1. Having a tendency to loosen or relax. --Milton.
      [1913 Webster]
   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.
      [1913 Webster]
WordNet (r) 3.0 (2006):
laxative
    adj 1: stimulating evacuation of feces [ant: costive]
    n 1: a mild cathartic
Moby Thesaurus II by Grady Ward, 1.0:
19 Moby Thesaurus words for "laxative":
   agar, aloes, aperient, bran, calomel, carminative, cascara,
   castor oil, cathartic, colocynth, diuretic, magnesia,
   mercurous chloride, mineral oil, mineral water, physic, purgative,
   purge, senna