The Collaborative International Dictionary of English v.0.48:
Abhorrer \Ab*hor"rer\, n. One who abhors. --Hume. [1913 Webster]WordNet (r) 3.0 (2006):
abhorrer n 1: a signer of a 1679 address to Charles II in which those who petitioned for the reconvening of parliament were condemned and abhorred