The Collaborative International Dictionary of English v.0.48:

Enema \En"e*ma\, n.; pl. L. Enemata. [L. enema, Gr. ?, fr. ?
   to send in; ? in + ? to send.] (Med.)
   An injection, or clyster, thrown into the rectum as a
   medicine, or to impart nourishment. --Hoblyn.
   [1913 Webster]

WordNet (r) 3.0 (2006):

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

Moby Thesaurus II by Grady Ward, 1.0:

88 Moby Thesaurus words for "enema":
   ablution, abstergent, aerosol, aspergil, aspergillum, atomizer,
   cathartic, cleaner, cleaning agent, cleaning out, cleaning solvent,
   cleanser, cleansing cream, clysma, clyster, cold cream,
   concentrate sprayer, cream, dentifrice, depurant, detergent,
   diuretic, douche, douching, elution, elutriation, emetic, flush,
   flushing, flushing out, fountain syringe, holystone, irrigation,
   lathering, lavabo, lavage, lavation, lavement, laving, lotion,
   mist concentrate sprayer, mopping, mopping up, mouthwash, nauseant,
   needle bath, nozzle, pumice stone, purgative, purge, purifier,
   rinse, rinsing, scouring, scrub, scrubbing, scrubbing up, shampoo,
   shower, shower bath, shower head, soap, soaping, solvent, sparge,
   sparger, sponge, sponging, spray, spray can, sprayer, sprinkler,
   sprinkler head, sprinkling system, swabbing, synthetic detergent,
   syringe, tooth powder, toothpaste, wash, washing, washing up,
   washout, washup, watercart, watering can, watering pot,
   wiping up