1. officiate jointly at (a Mass):"the pro-nuncio will concelebrate Mass with bishops from Wales"
Word Originlate 16th century (in the sense ‘celebrate together’): from Latin concelebrat- ‘celebrated together’, from the verb concelebrare, from con- ‘together’ + celebrare (see celebrate). The sense ‘officiate jointly at (a Mass)’ dates from the mid 19th century.