The Collaborative International Dictionary of English v.0.48:

Hexapla \Hex"a*pla\, n. Etym. pl., but syntactically sing. [NL.,
   fr. Gr. ?, fr. ?, contr. ?, sixfold.]
   A collection of the Holy Scriptures in six languages or six
   versions in parallel columns; particularly, the edition of
   the Old Testament published by Origen, in the 3d century.
   [1913 Webster]