What does embolus mean?
An embolus is a mass of material—most often a fragment of a blood clot—that breaks loose and travels through the bloodstream until it becomes lodged in a vessel too narrow for it to pass, blocking blood flow. Other substances can also act as emboli, including air bubbles, fat globules released after bone fractures, clumps of tumor cells, or amniotic fluid. The resulting obstruction is called an embolism, and its consequences depend on where the vessel is blocked: a pulmonary embolus in the lung arteries can be fatal within minutes, while one reaching the brain causes ischemic stroke. Clinicians distinguish an embolus from a thrombus, which is a clot that forms and stays anchored at its site of origin. The plural is emboli. Though rarely used outside medicine, the word is essential vocabulary for understanding news reports of strokes, surgical complications, and cardiovascular emergencies.
nounA mass of matter, such as a detached blood clot, air bubble, or fat globule, that travels through the bloodstream or lymphatic system until it lodges in a vessel and obstructs circulation.
- A detached mass — such as a blood clot fragment, air bubble, fat globule, or clump of cells — carried by the blood or lymph until it lodges in and obstructs a vessel.
- (Rare, non-medical) A plug or wedge-shaped stopper; an insertion or something interposed.
"The surgeon identified an embolus lodged in the pulmonary artery as the cause of the patient's sudden collapse."
"An embolus dislodged from a deep vein in her leg traveled to the lungs, producing a life-threatening pulmonary embolism."
"In patients with atrial fibrillation, small emboli can form in the heart's chambers and travel onward to the brain, causing stroke."
The standard plural follows the Latinized Greek second-declension pattern (-us → -i). The anglicized 'emboluses' appears occasionally in informal writing but is uncommon in medical literature.
"Multiple emboli were detected in both lungs during the CT scan."
Every embolus is a traveler with a ticket to nowhere — it drifts through your bloodstream until it wedges somewhere it can do real damage.
Reviewed by Deb Chak, Editor. AI-assisted content curated by RJS Tech Solutions LLP.
Etymology of embolus
The word embolus comes via New Latin from the Greek émbolos, meaning 'plug,' 'stopper,' or 'piston,' derived from em- ('in') and ballein ('to throw' or 'to cast'). The same Greek root gives English 'embole,' 'embolism,' and even 'symbol,' which originally referred to a token thrown together for comparison. The medical sense of a traveling mass blocking a vessel became established in the mid-nineteenth century, particularly through the work of Rudolf Virchow, who clarified the relationship between thrombosis and embolism.
Related word forms
How embolus is actually used
Embolus is a formal medical term used almost exclusively in clinical and academic contexts. The plural is emboli (/ˈɛmbəlaɪ/), following its Greek-derived Latin declension, though 'emboluses' occasionally appears in lay writing. It carries no emotional connotation outside its serious clinical associations. In everyday speech about blockages, people more often say 'clot' or refer to the condition (e.g., 'a pulmonary embolism') rather than the object itself.
Easily confused with embolus
A thrombus is a blood clot that forms and remains attached to the vessel wall where it developed, while an embolus is any material (often a fragment of thrombus) that breaks free, travels through the bloodstream, and lodges elsewhere.
An embolus is the traveling mass itself, whereas embolism is the medical condition or event caused when that mass blocks a vessel.