titer /tī′tər/ [Fr, titre, to make a standard,] , 1. the normality of a solution or substance, determined by titration to find the equivalence of two reactants. 2. the extent to which an antibody can be diluted before losing its power to react with a specific antigen. 3. the highest dilution of a serum that causes clumping of bacteria or other visible reaction. Also spelled titre.
