embolus

noun2

1. •
   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. •
   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