A chronic ulcer of the skin caused by prolonged pressure on it (as in bedridden patients) WordNet 3.0 & Open English WordNet

Pressure ulcers, also known as pressure sores, bed sores or pressure injuries, are localised damage to the skin and/or underlying tissue that usually occur over a bony prominence as a result of usually long-term pressure, or pressure in combination with shear or friction. Wikipedia

Chronic ulcer of skin where the ulcer is an ulceration of tissue deprived of adequate blood supply by prolonged pressure Wikidata

Lesion of the skin and underlying tissue caused by prolonged pressure, especially areas where skin is directly over bone. OmegaWiki

A lesion caused by unrelieved pressure to any part of the body, especially portions over bony or cartilaginous areas, such as frequently develops on a person confined to a bed by infirmity. Wiktionary

Lesion caused by pressure. Wiktionary (translation)