adjectiveAncient Greek History
Of a festival, etc.: occurring every fifth year.
According to modern calculation actually every fourth year, as both of two consecutive occurrences were counted.
Late 19th century; earliest use found in Journal of Hellenic Studies. From Hellenistic Greek πεντετηρικός occurring every fifth year (counting inclusively) from ancient Greek πεντετηρίς festival celebrated every fifth year (from πεντέτης of five years from πέντε five + ἔτος year) + -ικός.