Chestburster

The Chestburster is the 3rd stage of a Xenomorph. After the Facehugger has implanted an embryo in a host's body, the embryo grows, and in a few hours bursts from the chest of a host. This is called a chestburster. It grows and molts into a full grown, adult alien. Queen Chestbursters take a longer time (a few days) before it bursts.