Definition of have at in US English:

have at

phrasal verb

  • Attempt or attack forcefully or aggressively.

    • ‘There are so many things to hit and detonate in this game and it's never been so much fun having at it with weapons.’
    • ‘Have at you, you English rogue!’
    • ‘One of his tips involves printing the manuscript out in full and having at it with one's favourite colour pen.’