What is the definition or description of: benign tumor?

"Growth" A tumor by any other name is a growth. It can be either benign or malignant, differentiated based upon the potential to spread (a malignant tumor is, by definition, a cancer). The best way to determine this is by a tissue biopsy, but we can make better predictions based on the organ of origin, physical exam, and x-ray findings.
A growth. Made up of typical cells, with few to no mitosis, and now disorganized growth, or disarray of maturity. Colon polyps fit the bill well.