Colon polyp: A benign tumor of the large intestine. Benign polyps do not invade nearby tissue or spread to other parts of the body. Benign polyps can easily be removed during colonoscopy and are not life threatening. If benign polyps are not removed from the large intestine, they can become malignant (cancerous) over time. Most cancers of the large intestine are believed to have developed from polyps.