noun
champion of children's sumo
Sumo term for the winner of a children's sumo tournament or the strongest child in a sumo group.
町内の子供相撲大会で、弟が腕白横綱になった。
My younger brother became the champion of the local children's sumo tournament.
Compound of 腕白 (わんぱく, 'naughty, mischievous child') and 横綱 (よこづな, 'yokozuna, grand champion in sumo'). The term refers to a child sumo champion.