practice session with a grand champion present
A sumo training session where a yokozuna (grand champion) participates, often attracting attention and raising the intensity of practice.
The practice session with the grand champion draws many spectators.
横綱 refers to the grand champion rank or the wrestler holding it, while 横綱稽古 specifically means a practice session where the yokozuna is present.
稽古 is general practice or training in traditional arts or sports; 横綱稽古 narrows it to sumo practice with a grand champion.
Compound of 横綱 (yokozuna, grand champion) and 稽古 (keiko, practice). The term is specific to sumo culture.