Dictionary.net

• Rapidly decreasing response to a drug or physiologically active agent after administration of a few doses. In immunology, it is the rapid immunization against the effect of toxic doses of an extract or serum by previous injection of small doses. (Dorland, 28th ed)

2010 - Medical Dictionary Database
By DataStellar Co., Ltd

• A tolerance or immunity acquired within a few minutes by the slow injection of a substance such as the extract of an organ.

1916 - Appleton's medical dictionary
By Smith Ely Jelliffe