To do as was promised in an agreement or bargain; to carry through with what one agreed to do. Also worded as "keep one's side of the bargain up." OK, I've delivered the cash as you instructed. Now you have to keep your side of the bargain! We've done the work on our side. I just hope their team keeps up their side of the bargain! My dad said he'd buy me a car if I got a 4.0 this semester, so I've got to ace this test if I want to keep my side of the bargain up.