expression, godan verb (-ru)
form a group; form a bunch; bunch up
Describes people or things gathering into a tight group or cluster, often with a sense of crowding together.
子供たちが校庭の隅で束になっている。
The children are bunched up in a corner of the schoolyard.
文句があるなら束になってかかってこい。
If you have complaints, come at me all together.