Contesting a bounce or ball up; used appositionally in "ruck contest". Rucks also used collectively either of ruckmen or of ruckmen and ruck rovers, and occasionally used in place of "followers" (including rovers too)
The situation formed when a runner is brought to ground and one or more members of each side are engaged above the ball, trying to win possession of it; a loose scrum
In the sport of rugby, a ruck is a situation where a group of players struggle for possession of the ball. ruck up if a piece of cloth rucks up, or if you ruck it up, it forms folds in an untidy way ruck sth⇔up