<haematology> The clear portion of any body fluid, the clear fluid moistening serous membranes.

2. Blood serum, the clear liquid that separates from blood on clotting.

3. Immune serum, blood serum from an immunised animal used for passive immunisation, an antiserum, antitoxin or antivenin.

This entry appears with permission from the Dictionary of Cell and Molecular Biology

(11 Mar 2008)