[se.rum] n, pl serums or se.ra [L, whey, wheylike fluid; akin to Gk oros whey] (1665) 1: the watery portion of an animal fluid remaining after coagulation: a (1): blood serum (2): antiserum b: whey c: a normal or pathological serous fluid (as in a blister)
2: the watery part of a plant fluid