embolus
noun (a blood clot, air bubble, or small object that causes an embolism 栓子（造成动脉栓塞的血块、气泡或小团块） Word Originmid 17th cent. (denoting something inserted or moving within another, specifically the plunger of a syringe): from Latin, literally ‘piston’, from Greek embolos ‘peg, stopper’. The current sense dates from the mid 19th cent.