slash at (someone or something)
1. To swing a cutting weapon in a forceful thrusting or sweeping stroke in the direction of someone. I picked up the knife and slashed at the would-be mugger to chase him away.
2. To cut something repeatedly with forceful thrusting or sweeping strokes. I kept slashing at the rope with my pocket knife, trying desperately to free my foot from the submerged boat.
slash (out) at someone
to thrust out at someone with a knife or something similar, with the intent of cutting. The attacker slashed out at his victim and then ran away. Max slashed at the cop with a pocketknife.