'beat up' definitions:

Definition of 'beat up'

From: WordNet
verb
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, beat up, work over]
verb
Gather; "drum up support" [syn: beat up, drum up, rally]