bed·sore / ˈbedˌsôr/ • n. a sore developed by an invalid because of pressure caused by lying in bed in one position. Also called decubitus ulcer.

bedsore (decubitus ulcer, pressure sore) (bed-sor) n. an ulcerated area of skin caused by continuous pressure on part of the body in a bedridden patient. Careful nursing is necessary to prevent local gangrene. The patient's position should be changed frequently, and the buttocks, heels, elbows, and other regions at risk kept dry and clean.
www.nice.org.uk/CG029 NICE guidance on the treatment of pressure sores