What is a fragment of thrombus that has broken free and entered the circulation called?

1. A thrombus is stationary and attached to the vessel wall. 2. When a portion breaks free and enters the circulation it is called an embolus. 3. If that travelling embolus becomes trapped it is then called an embolism. 4. Lodged in the heart, brain or lungs it produces a heart attack, a stroke or a pulmonary embolism. 5. A rouleaux is a harmless stack of red cells in a wide vessel, so it is not a clot fragment at all. _Source: OpenStax Anatomy and Physiology (CC BY 4.0), Ch 18 "The Cardiovascular System: Blood", section 18.5 Hemostasis_