have a good arm
To be capable of throwing something powerfully and/or a far distance. Often said of pitchers in baseball. Keith should be our new pitcher—he has a good arm. Wow, you have a good arm—I can't believe you threw that water bottle all the way over here.
have a good arm
Fig. to have a strong and conditioned arm for sports, especially pitching in baseball. Perry had a good arm, but he often pitched wide of the plate.