embolus

Etymology

The term was coined in 1848 by Rudolf Virchow From Latin embolus (“piston”), from Ancient Greek ἔμβολος (émbolos, “peg, stopper”).

noun

1. (pathology) An obstruction causing an embolism: a blood clot, air bubble or other matter carried by the bloodstream and causing a blockage or occlusion of a blood vessel.
2. (zoology) The structure on the end of the palp of male arachnids which contains the opening to the ejaculatory duct.
   Those spiders with a simple bulb insert most of this; those with a complex palp insert only the embolus, which in some species is very long […] 1996, Michael J Roberts, Spiders of Britain and Northern Europe, Collins, published 1996, page 22