immunoglobulin: Meaning and Definition of

im•mu•no•glob•u•lin

1. any of several classes of structurally related proteins that function as antibodies or receptors and are found in plasma and other body fluids and in the membrane of certain cells. Cf. IgA, IgD, IgE, IgG, and
2. the fraction of the blood serum containing antibodies.
3. an antibody. Abbr.: Ig