Something is carcinogenic if it has the potential to cause cancer. Asbestos, a material that was frequently used for insulation, was found to be carcinogenic, leading to laws regulating its use.
To correctly pronounce carcinogenic, accent the fourth syllable: "car-sih-nuh-JEN-ick." Carcinogenic is related to the noun carcinogen, meaning "a cancer-causing substance." Both words come from carcinoma, or "malignant tumor" and -gen, a suffix that means "something produced." So something that is carcinogenic produces malignant tumors — cancer.