se ‧ rum /ˈsɪərəm $ ˈsɪr-/ BrE AmE noun ( plural serums or sera /-rə/) [uncountable and countable]
[ Date: 1600-1700 ; Language: Latin ]
1 . medical a liquid containing substances that fight infection or poison, that is put into a sick person’s blood ⇨ ↑ vaccine
2 . technical the thin part of blood or the liquid from a plant