What is the term for fluid, such as pus, that leaks out of an infected wound?

The term for fluid that leaks out of an infected wound is "exudate." Exudate refers specifically to fluid that has escaped from blood vessels due to inflammation and is typically rich in proteins and cellular debris. This type of fluid commonly occurs in response to infection or injury and is often thick or cloudy, containing substances such as pus, which is indicative of infection.

In contrast, transudate refers to a more watery fluid that is typically clear and low in protein, occurring in situations such as non-inflammatory conditions, like heart failure or cirrhosis. Excretion generally refers to the process of eliminating waste products from the body, such as urine or sweat, while serum is the liquid component of blood after the clotting factors have been removed, which is not specific to infection or wound leakage. Therefore, exudate is the correct term for the fluid described in the question.