swelling

an abnormal protuberance or localized enlargement

something that bulges out or is protuberant or projects from its surroundings; "the gun in his pocket made an obvious bulge"; "the hump of a camel"; "he stood on the rocky prominence"; "the occipital protuberance was well developed"; "the bony excrescence between its horns"

the increase in volume of certain substances when they are heated (often accompanied by release of water)