lowest-ranked wrestler in the top division
Sumo term: the wrestler at the very bottom of the makuuchi (top) division rankings.
The lowest-ranked makuuchi wrestler this tournament is the one who came up from the juryo division last tournament.
Compound of 幕 (maku, 'curtain', referring to the makuuchi division) and 尻 (shiri/jiri, 'bottom' or 'end'), literally 'the bottom of the makuuchi'.