or bunch together
If people or things bunch up or bunch together , or if you bunch them up or bunch them together , they move close to each other so that they form a small tight group.
They were bunching up, almost treading upon each other’s heels...
People were bunched up at all the exits...
If they need to bunch aircraft more closely together to bring in one that is short of fuel, they will do so.
PHRASAL VERB : V P , V-ed P , V n P