Source : WordNet®

beat up
     v 1: give a beating to; subject to a beating, either as a
          punishment or as an act of aggression; "Thugs beat him
          up when he walked down the street late at night"; "The
          teacher used to beat the students" [syn: {beat}, {work
          over}]
     2: gather; "drum up support" [syn: {drum up}, {rally}]