protuberance; protruding object
General term for something that sticks out from a surface; used in everyday and technical contexts.
There are several small protrusions on this wall.
umbo
Biology term for a knob-like protuberance, such as on a shell or spore.
The protrusion on this shell is called an umbo.
Compound of 突起 (とっき, 'protrusion') + 物 (ぶつ, 'thing').