The Collaborative International Dictionary of English v.0.48:

Clyster \Clys"ter\, n. [L., fr. G. ?. fr. ? to wash off or out;
   akin to Goth. hl[=u]trs pure, G. lauter: cf. F. clyst[`e]re]
   (Med.)
   A liquid injected into the lower intestines by means of a
   syringe; an injection; an enema.
   [1913 Webster]

   Clyster pipe, a tube or pipe used for injections.
      [1913 Webster]

WordNet (r) 3.0 (2006):

clyster
    n 1: an injection of a liquid through the anus to stimulate
         evacuation; sometimes used for diagnostic purposes [syn:
         enema, clyster]