abstrusion
n. C2 Proficiency ab·stru·sion
n. a part that sticks out or is pushed forward. It is an old word for something that is not level with the rest.
n. a part or projection that sticks out or is pushed forward; a protuberance. Archaic in modern usage, it is primarily found in historical or technical contexts.
Borrowed from Latin abstrusio. See abstruse.