The Collaborative International Dictionary of English v.0.48:

Excretion \Ex*cre"tion\, n. [Cf. F. excr['e]tion.]
   1. The act of excreting.
      [1913 Webster]

            To promote secretion and excretion.   --Pereira.
      [1913 Webster]

   2. That which is excreted; excrement. --Bacon.
      [1913 Webster]

WordNet (r) 3.0 (2006):

excretion
    n 1: the bodily process of discharging waste matter [syn:
         elimination, evacuation, excretion, excreting,
         voiding]
    2: waste matter (as urine or sweat but especially feces)
       discharged from the body [syn: body waste, excretion,
       excreta, excrement, excretory product]

Moby Thesaurus II by Grady Ward, 1.0:

45 Moby Thesaurus words for "excretion":
   cleaning out, clearance, clearing, defecation, depletion,
   discharging cargo, drainage, draining, effusion, egress,
   elimination, emptying, evacuation, exfiltration, exhausting,
   exhaustion, external secretion, extravasation, exudation,
   filtering, filtration, internal secretion, lacrimation, lactation,
   leaching, lixiviation, off-loading, ooze, oozing, percolating,
   percolation, removal, secernment, secreta, secretion, seep,
   seepage, straining, transudation, unloading, venting, voidance,
   voiding, weep, weeping