Source : Webster's Revised Unabridged Dictionary (1913)

Defecation \Def`e*ca"tion\, n. [L. defaecatio: cf. F.
   d['e]f['e]cation.]
   1. The act of separating from impurities, as lees or dregs;
      purification.

   2. (Physiol.) The act or process of voiding excrement.

Source : WordNet®

defecation
     n : the elimination of fecal waste through the anus [syn: {laxation},
          {shitting}]