What's the noun for thrombophlebitis? Here's the word you're looking for.
thrombus
(hematology) A blood clot formed from platelets and other elements; that forms in a blood vessel in a living organism, and causes thrombosis or obstruction of the vessel at its point of formation or travel to other areas of the body.
“Ginger is therefore a good herb for people with a history of stroke or atherosclerosis, thrombophlebitis and varicose veins.”
“Patients with a history of deep vein thrombosis or thrombophlebitis who have surgery should receive perioperative subcutaneous heparin prophylaxis.”
“The infection may spread to involve the parapharyngeal or retropharyngeal spaces with complications including mediastinitis and septic thrombophlebitis.”