The Graeco-Babyloniaca (singular: Graeco-Babyloniacum) are clay tablets written in the Sumerian or Akkadian languages using cuneiform on one side with transliterations in the Greek alphabet on the other.
Quoting Edmond Sollberger:
As worded by M. J. Geller, they indicate that both Babylonian languages "written in cuneiform characters were still legible in the Seleucid and Parthian periods in Mesopotamia".