A blow

Going Blow for Blow can mean Going for a punch while being handed a punch For example let's say you are person A and person A hits Person B. Person B hits Person A right after Person A sends a punch to Person B, and it's just this repeated process of handing punches right to each other without any sort of defense or hesitation. We also have blow for blow in a figurative sense, a prank war is a great example of this. As Person A rips a page out of Person B's favorite book, Person B breaks Person A's favorite pencil. It's just a constant battle of retaliation