External pyocephalus, also known as external occipital protuberance, is a prominent bony bump located at the back of the skull. Commonly referred to as the "knob" or "bump" on the back of the head, it serves as an attachment site for ligaments and muscles involved in head and neck movements. Although often associated with external pyocephalus, several synonyms can be used to refer to this anatomical feature. Some alternative terms include occipital bun, occipital protuberance, occipital crest, or occipital boss. These synonyms highlight the various ways people describe this specific characteristic, making it easier to communicate about and discuss the external pyocephalus in medical or informal settings.