Lysis means dissolution, liquefaction. Thrombus is a blood clot. Thus, thrombolysis means chemical dissolution of blood clots by drugs.
The best known drugs for this purpose are streptokinase and TPA.
These drugs are given intravenously in certain cases of myocardial infarction (heart attack) to dissolve the blood clot, which together with a lipid plaque in the arterial wall totally occlude it.
One of the undesired inherent side effects of these drugs is that they can cause bleeding. Therefore, there are strict indications for the administration of such drugs.