The Collaborative International Dictionary of English v.0.48:

Oblocutor \Ob*loc"u*tor\, n. [L. oblocutor, obloquutor, fr.
   obloqui, oblocutus, to speak against; ob (see Ob-) + loqui
   to speak. See Loquacious.]
   A disputer; a gainsayer. [Obs.] --Bale.
   [1913 Webster]