Source : WordNet®

pile up
     v 1: collect or gather; "Journals are accumulating in my office";
          "The work keeps piling up" [syn: {accumulate}, {cumulate},
           {conglomerate}, {gather}, {amass}]
     2: arrange into piles or stacks; "She piled up her books in my
        living room" [syn: {heap up}, {stack up}]
     3: get or gather together; "I am accumulating evidence for the
        man's unfaithfulness to his wife"; "She is amassing a lot
        of data for her thesis"; "She rolled up a small fortune"
        [syn: {roll up}, {collect}, {accumulate}, {amass}, {compile},
         {hoard}]