You have one less leg than other members of your species, whether through accident, injury, or birth. For a bipedal species, missing a leg puts you at a pretty serious disadvantage, as you will need to rely on a crutch or cane to support your weight, or use a hoverchair to get around. Your other leg works fine, but they’re best in pairs.
You suffer a 2D+0 penalty to all Run, Dodge, Brawl, and Melee rolls.
You may buy out this disadvantage at a cost of 30CP, if you wish to replace your missing leg with a prosthetic, or if you have found a suitable organic replacement and a doctor willing to attach it for you.