Source : Webster's Revised Unabridged Dictionary (1913)

Laxation \Lax*a"tion\, n. [L. laxatio, fr. laxare to loosen, fr.
   laxus loose, slack.]
   The act of loosening or slackening, or the state of being
   loosened or slackened.

Source : WordNet®

laxation
     n 1: the elimination of fecal waste through the anus [syn: {defecation},
           {shitting}]
     2: the act of making something less tight [syn: {loosening}]
        [ant: {tightening}]