noun
ring-purification ceremony
A Shinto ceremony held before a sumo tournament to purify the dohyo and pray for safety.
土俵祭りは本場所の前日に行われる。
The ring-purification ceremony is held the day before the main tournament.
土俵 is the sumo ring itself; 土俵祭り is the specific purification ceremony for it.
Compound of 土俵 (dohyo, sumo ring) and 祭り (matsuri, festival/ceremony).