A protrusion is something that sticks out — or the fact of sticking out. You might notice one on a wall, a bone, or a piece of machinery. Doctors talk about a disc protrusion in the spine, when part of the disc bulges out of place. Engineers and geologists use it too. It is the noun that sits beside the verb protrude. In everyday English it still sounds a little technical; a child would probably just say bump, or a bit that sticks out. Though actually, once you are in a hospital or a workshop, protrusion is the normal word, not a fancy one.

突出物；突起。脊椎的情況，台灣常說「椎間盤突出」。