Entry 1 sense Webster, 1913 carcinogen /(kär*sĭn"ō̇*jĕn)/ · car·cin·o·gen · IPA /kɑɹˈsɪnəd͡ʒən/ 01 n. Any substance that produces cancer; as, to test for carcinogens in the drinking water. 1. Any substance that produces cancer; as, to test for carcinogens in the drinking water.