Source : WordNet®

bunch up
     v 1: form into a bunch; "The frightened children bunched together
          in the corner of the classroom" [syn: {bunch together},
          {bunch}]
     2: gather or cause to gather into a cluster; "She bunched her
        fingers into a fist"; "The students bunched up at the
        registration desk" [syn: {bunch}, {bundle}, {cluster}, {clump}]