noun

• The clear yellowish liquid obtained upon separating whole blood into its solid and liquid components after it has been allowed to clot.
• Blood serum from the tissues of immunized animals, containing antibodies and used to transfer immunity to another individual.
• A watery liquid from animal tissue, especially one that moistens the surface of serous membranes or that is exuded by such membranes when they become inflamed, such as in edema or a blister.
• The watery portion of certain animal fluids like blood, milk, etc; whey.
• (skincare) An intensive moisturising product to be applied after cleansing but before a general moisturiser.