The Collaborative International Dictionary of English v.0.48:
Disprover \Dis*prov"er\, n. One who disproves or confutes. [1913 Webster]WordNet (r) 3.0 (2006):
disprover n 1: a debater who refutes or disproves by offering contrary evidence or argument [syn: rebutter, disprover, refuter, confuter]