The Collaborative International Dictionary of English v.0.48:

Abnegator \Ab"ne*ga`tor\, n. [L.]
   One who abnegates, denies, or rejects anything. [R.]
   [1913 Webster]

WordNet (r) 3.0 (2006):

abnegator
    n 1: one who gives up or relinquishes or renounces something