| an arrangement of five objects, as trees, in a square or rectangle, one at each corner and one in the middle. |
| an extraordinary or unusual thing, person, or event; an exceptional example or instance. |
antigen an·ti·gen (ān'tĭ-jən)
n.
Any of various substances, including toxins, bacteria, and the cells of transplanted organs, that when introduced into the body stimulate the production of antibodies. Also called allergen, immunogen.
| antigen (ān'tĭ-jən) Pronunciation Key
A substance that stimulates the production of an antibody when introduced into the body. Antigens include toxins, bacteria, viruses, and other foreign substances. Compare antibody. See Note at blood type. |