The Collaborative International Dictionary of English v.0.48:

Defecator \Def"e*ca`tor\, n.
   That which cleanses or purifies; esp., an apparatus for
   removing the feculencies of juices and sirups. --Knight.
   [1913 Webster]

WordNet (r) 3.0 (2006):

defecator
    n 1: a person who defecates [syn: defecator, voider,
         shitter]