Final answer:
A platelet plug reinforced with fibrin, which may include trapped erythrocytes, is called a fibrin clot or fibrin plug.
Step-by-step explanation:
A platelet plug reinforced with fibrin, which may include trapped erythrocytes, is called a fibrin clot or fibrin plug. When a blood vessel is injured, platelets clump together at the site of injury and form a plug to stop bleeding. The plug is strengthened by the formation of fibrin, a protein that forms a mesh around the platelets.