Θησεῖα Save Θησεῖα, festival of Theseus Could not find Θησείοις in Logeion dictionaries. Θησείοις Proper-name noun: neuter dative plural of Θησεῖα Θησείοις Proper-name noun: neuter dative plural of Θησεῖον See Θησείοις in Morpho No dictionary entries for this word.