Collins COBUILD Advanced Learner's English Dictionary - bunch up

or bunch together If people or things bunch up or if you bunch them up, they move close to each other so that they form a small tight group. Bunch together means the same as bunch up. 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