LSJ Gloss:ἑορτάζωto keep festivalDodson:ἑορτάζωI keep a feastI take part in a festival, keep a feast (allegorically).
TBESG:ἑορτάζωto keep a festivalG:V ἑορτάζω (< ἑορτή), [in LXX for חָגַג ;] to keep festival: 1Co.5:8.† (AS)