The antonyms for "out-run" can be classified into three main categories: slow down, lag behind, and lose. When you slow down, you do the opposite of out-run. You might even come to a stop or pause. When you lag behind, you stay behind the person or thing running ahead of you. There may be several reasons for this, including fatigue or injury. Finally, the opposite of out-run can be to lose. In this context, it can mean to lose the race, to lose the battle, or to lose the argument. Thus, whether it's slowing down, lagging behind, or losing, there are plenty of antonyms for out-run.