cyclooxygenase n either of two related enzymes that control the production of prostaglandins and are blocked by aspirin Usage(s) Chances are you've had plenty of dealings with those irksome little enzymes cyclooxygenase 1 and cyclooxygenase 2, better known as cox-1 and cox-2. It does so by blocking an enzyme called cyclooxygenase, or COX, that's involved in the manufacture of prostaglandins. Synonym(s) Cox