n. (pl. sera or serums)
1. a an amber-coloured liquid that separates from a clot when blood coagulates. b whey.
2 Med. blood serum (usu. from a non-human mammal) as an antitoxin or therapeutic agent, esp. in inoculation.
3 a watery fluid in animal bodies.
Phrases and idioms:
serum sickness a reaction to an injection of serum, characterized by skin eruption, fever, etc.
Etymology: L, whey