The Collaborative International Dictionary of English v.0.48:
Refuter \Re*fut"er\ (r[-e]*f[=u]t"[~e]r), n. One who, or that which, refutes. [1913 Webster]WordNet (r) 3.0 (2006):
refuter n 1: a debater who refutes or disproves by offering contrary evidence or argument [syn: rebutter, disprover, refuter, confuter]