The Collaborative International Dictionary of English v.0.48:

Transfrete \Trans*frete"\, v. i. [L. transfretare; trans across,
   over + fretum a strait: cf. OF. transfreter.]
   To pass over a strait or narrow sea. [Written also
   transfreight.] [Obs.] --E. Hall.
   [1913 Webster] Transfuge