[kraws-ri-zis-tuh
ns, kros-] 
| 1. | immunologic resistance to the pathogenic effects of a microorganism because of previous exposure to another species or type having cross-reactive antigens. |
| 2. | resistance to the effects of a substance, as that of an insect population to an insecticide or a bacterial strain to an antibiotic, stimulated by exposure and adaptation to a similar or related substance. |