1. A wall that forms the side of a building or other structure. OK, class, line up at the side wall! At every school dance, Peggy found herself drawn to boys who leaned against the side walls and looked as if they had no interest in being there.

2. The side of the tire on a motor vehicle. A: "How will I know what kind of tires to get?" B: "Well, there's information printed on the side wall of a tire—you can look there to find out more about the ones you currently have."