In medicine, an embolism (plural embolisms; from the Greek ἐμβολισμός "insertion") is the event of lodging of an embolus (a detached intravascular mass capable of clogging arterial capillary beds at a site far from its origin) into a narrow capillary vessel of an arterial bed which causes a blockage (vascular occlusion) in a distant part of the body. This is not to be confused with a thrombus which blocks at the site of origin.
Embolization is a procedure that purposely creates such a lodging and occlusion of specific blood vessels with thrombo-emboli in order to deprive tumors (or other pathologic processes) of their perfusion (blood supply).