Is it ensure, insure, or assure?
1690s, Modern Latin, from Greek thrombos "lump, piece, clot of blood, curd of milk."
thrombus throm·bus (thrŏm'bəs)
n. pl. throm·bi (-bī)
A fibrinous clot formed in a blood vessel or in a chamber of the heart.
Plural thrombi (thrŏm'bī')
A clot consisting of fibrin, platelets, red blood cells, and white blood cells that forms in a blood vessel or in a chamber of the heart and can obstruct blood flow. The rupture of atherosclerotic plaques can cause arterial thrombosis (the formation of thrombi), while tissue injury, decreased movement, oral contraceptives, prosthetic heart valves, and various metabolic disorders increase the risk for venous thrombosis. A thrombus in a coronary artery can cause a heart attack. Compare embolus.