The Collaborative International Dictionary of English v.0.48:

Dilogy \Dil"o*gy\, n.; pl. Dilogies. [L. dilogia, Gr. ?, fr. ?
   doubtful; di- = di`s- twice + ? to speak.] (Rhet.)
   An ambiguous speech; a figure in which a word is used an
   equivocal sense. [R.]
   [1913 Webster]