Sekiwake (関脇) is the third highest rank in professional sumo wrestling, and is one of the so-called sanyaku ranks. It is believed to come from guarding the Ozeki (大関 or 関) at his side (脇).
It represents the highest rank a wrestler can achieve by continuously making a majority of wins in tournaments, as there are special promotion criteria for the next highest rank of Ozeki. Unlike the higher ranks of Ozeki and Yokozuna, one will lose the rank immediately after having a makekoshi tournament (more losses than wins).
Promotion to sekiwake depends on either a space being available, which is quite common, or having a record in the previous tournament that is very convincing, typically 10-5 or better as a komusubi.
He may also be called on to represent the wrestlers on behalf of the Sumo Association at other events, especially if the number of Ozeki and Yokozuna is low.
If this is the highest rank a wrestler reaches, even if it is only for one tournament, he will always be referred to as "former sekiwake (ring name)" after his retirement, which is an indicator of a successful sumo career, whilst not achieving the exceptional standards of the highest two ranks..