An embolus (plural emboli; from the Greek ἔμβολος "clot, lit. ram") is any detached, traveling intravascular mass (solid, liquid, or gaseous) carried by circulation, which is capable of clogging arterial capillary beds (create an arterial occlusion) at a site distant from its point of origin.


Illustration depicting embolism from detached thrombus
By contrast there are non-traveling blockages that develop locally from vascular trauma or epithelial pathology and vascular inflammation — like atheroma, thrombi. However, if a thrombus breaks loose from its genesis site it becomes a thrombo-embolus and if not broken down during transit, may cause embolism(s).

The term was coined in 1848 by [[Rudolf Ludwig Karl Virchow]].