A thrombus is a blood clot that forms inside a vessel in the body and stays there. If thrombi (the plural of thrombus) break loose and move to another part of the body, they are then called emboli (the plural of embolus).

The related medical condition where a thrombus has broken free and travelled to lodge in another part of the body is called a thromboembolism.

Read more about blood clots here.