Final answer:
Thrombosis is the medical term for a blood clot obstructing the vessel where it formed. A dislodged thrombus is called an embolus, leading to embolism if it causes a blockage.
Step-by-step explanation:
The medical term for an abnormal condition in which a blood clot forms in a vessel and obstructs it at the site of its formation is thrombosis. A thrombus is an aggregation of clotting components, such as platelets, erythrocytes (red blood cells), and possibly white blood cells (WBCs), which are trapped within a mass of fibrin strands. If a thrombus becomes dislodged and travels through the bloodstream, it is known as an embolus, and when it lodges in a vessel and causes a blockage, this is termed an embolism. Embolism can lead to severe complications such as heart attacks, strokes, or pulmonary embolisms, which are medical emergencies.