The Collaborative International Dictionary of English v.0.48:
Pythian \Pyth"i*an\, a. [L. Pythius, Gr. ? belonging to Pytho,
the older name of Delphi and its environs: cf. F. pythien.]
Of or pertaining to Delphi, to the temple of Apollo, or to
the priestess of Apollo, who delivered oracles at Delphi.
Pythian games (Gr. Antiq.), one of the four great national
festivals of ancient Greece, celebrated near Delphi, in
honor of Apollo, the conqueror of the dragon Python, at
first once in eight years, afterward once in four.