1. An informal shortening of "speedometer." I think putting those big new tires on your car messed up the speedo. Most speedos are digital now, making them much easier to recalibrate.

2. A tight-fitting male swimsuit that resembles briefs. The term is taken from the brand name of a manufacturer known for making such swimsuits. I used to be embarrassed wearing a speedo to the pool, but it made such a difference while I was swimming laps that I soon stopped caring. Look at that meathead, strutting around the beach with his oiled-up muscles and his tiny little speedo.