Search Result for "antigen": 
Wordnet 3.0

NOUN (1)

1. any substance (as a toxin or enzyme) that stimulates an immune response in the body (especially the production of antibodies); 



WordNet (r) 3.0 (2006):

antigen
    n 1: any substance (as a toxin or enzyme) that stimulates an
         immune response in the body (especially the production of
         antibodies)