Medical term for a mass (such as a blood clot or air bubble) that travels through the bloodstream and blocks a vessel.
肺塞栓症は、肺動脈に栓子が詰まる病気です。
Pulmonary embolism is a disease in which an embolus blocks the pulmonary artery.
From 栓 (plug, stopper) + 子 (small thing, child), a coined medical term for an embolus. The exact derivation is uncertain, but the kanji suggest a small plug-like object.