Ulcerous is a medical term used to describe a condition in which open sores or ulcers form on the skin or mucous membranes. CANKER is another term for an ulcer, and is typically used to describe ulcers that form inside the mouth. Ulcerous can also refer to any type of sore or lesion that is caused by inflammation or infection. Ulcers can be caused by a variety of factors, including bacteria, viruses, fungi, and even stress. Treatment for ulcers typically involves antibiotics, antifungal medications, and topical creams.