Keloid: A scar that rises quite abruptly above the rest of the skin. It is irregularly shaped, usually pink to red in color, tends to enlarge progressively, and may be harder than the surrounding skin. Keloids are a response to trauma, such as a cut to the skin. In creating a normal scar, connective tissue in the skin is repaired by the formation of collagen. Keloids arise when extra collagen forms. Susceptibility to keloids is genetic, and keloids are particularly common in people of African descent.