The Collaborative International Dictionary of English v.0.48:

Effacement \Ef*face"ment\, n. [Cf. F. effacement.]
   The act if effacing; also, the result of the act.
   [1913 Webster]

WordNet (r) 3.0 (2006):

effacement
    n 1: shortening of the uterine cervix and thinning of its walls
         as it is dilated during labor
    2: withdrawing into the background; making yourself
       inconspicuous [syn: effacement, self-effacement]