Chestbursters are immature xenomorphs from the Alien series of films.So called because of their unfortunate habit of erupting from a host's chest (where they have been implanted by a facehugger), killing them in the process. At birth they are about three foot long, and snakelike, except for the distinctive alien elongated head. They hide and rapidly grow to into a full-sized xenomorph, shedding their skin in the process. The chestburster scene from Alien is one of the best scenes in the film