noun. the existence or development of a blood clot within a blood vessel, inclusive of blood vessels inside the heart. Development of a blood clot within a vein is referred to as venous thrombosis. Thrombosis is likely to form where blood flow is inhibited by illness, trauma, damage, or a foreign compound. A thrombosis within the brain can elicit a thrombotic stroke or cerebrovascular accident.
THROMBOSIS: "Certain birth control pills have been linked to the increased risk of pulmonary thrombosis."