The adjective xiphoid describes any part of the body that's shaped like a sword. It's mostly used for the xiphoid process, a small, triangular part of the human breastbone.
Your xiphoid process is located in the middle of your chest, where your sternum and lower ribs meet. This anatomical feature got its name from the swordlike shape of its lower edge; the Greek root, xiphos, means "sword." You could also use xiphoid as a fancy way to describe anything in the curved shape of a sword, like the xiphoid leaves of your favorite houseplant, but it's unlikely anyone will understand what you mean!