A cicatrice is a scar, the mark left on your skin when a cut, scrape, or burn has started to heal. If you wipe out on your bike you might end up, weeks later, with a cicatrice on your knee.
It's much more common to use the word scar, but you can also use cicatrice, or cicatrix, as it's also spelled. Often a cicatrice will fade over time, as the initial wound completes the healing process, but sometimes a cicatrice can stick around for the rest of your life as a reminder of your youthful skateboard adventures. Cicatrice comes from the Latin cicatrix, "scar."