What is "graeco-armenian"

Graeco-Armenian (also Helleno-Armenian) is the hypothetical common ancestor of the Greek and Armenian languages that postdates the Proto-Indo-European language (PIE). Its status is comparable to that of the Italo-Celtic grouping: each is widely considered plausible without being accepted as established communis opinio. The hypothetical Proto-Graeco-Armenian stage would need to date to the 3rd millennium BC, only barely differentiated from either late PIE or Graeco-Armeno-Aryan.