Definition of beat up on in US English:

beat up on

phrasal verb

North American
  • 1Assault and severely injure someone by hitting, kicking, or punching them repeatedly.

    ‘he apparently loves fighting so much that he beats up on his own teammates’
  • 2Abuse someone verbally.

    ‘they like listening to them beat up on the president’
    assault, attack, mug, batter, thrash, pummel, pound
    View synonyms