The Collaborative International Dictionary of English v.0.48:

Aperient \A*pe"ri*ent\, a. [L. aperiens, p. pr. of aperire to
   uncover, open; ab + parire, parere, to bring forth, produce.
   Cf. Cover, Overt.] (Med.)
   Gently opening the bowels; laxative. -- n. An aperient
   medicine or food. --Arbuthnot.
   [1913 Webster]

WordNet (r) 3.0 (2006):

aperient
    adj 1: mildly laxative
    n 1: a purging medicine; stimulates evacuation of the bowels
         [syn: purgative, cathartic, physic, aperient]