serum
noun
se·rum
| \ ˈsir-əm
\
\
plural sera\ ˈsir-ə
\
or serums
\
or serums
Definition of serum
(Entry 1 of 2)
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
3
: a usually lightweight cosmetic preparation especially for use on the face
specifically
: a typically water-based, often concentrated preparation that lacks lubricating and thickening agents
an antiaging facial serum