The Collaborative International Dictionary of English v.0.48:

Hellenistic \Hel`le*nis"tic\, Hellenistical \Hel`le*nis"tic*al\,
   a. [Cf. F. Hell['e]nistique.]
   Pertaining to the Hellenists.
   [1913 Webster]

   Hellenistic language, Hellenistic dialect, or
   Hellenistic idiom, the Greek spoken or used by the Jews who
      lived in countries where the Greek language prevailed; the
      Jewish-Greek dialect or idiom of the Septuagint.
      [1913 Webster]

WordNet (r) 3.0 (2006):

Hellenistical
    adj 1: relating to or characteristic of the classical Greek
           civilization [syn: Hellenic, Hellenistic,
           Hellenistical]