means an antibody that specifically binds and neutralizes a toxin, disarming it without necessarily killing the organism that made it.

from coined in the 1890s from anti- (against) plus toxin, right after Emil von Behring and Shibasaburo Kitasato discovered that blood serum from an animal exposed to diphtheria toxin could neutralize it in another animal; Behring won the first-ever Nobel Prize in Medicine for it in 1901.