“Elongated skull” is a term used to describe the shape of the back of one’s head. As the name implies, an elongated skull is a skull shape which is, well, elongated. People who possess this amusing phenotype have a large/prominent occipital protuberance, which gives the skull a stretched-out look when viewed from the side (xD).
“That guy has more of an elongated skull than an ancient Egyptian pharaoh!”