bedsore(n = noun.state) decubitus ulcer, pressure sore - a chronic ulcer of the skin caused by prolonged pressure on it (as in bedridden patients);
is a kind of ulcer, ulceration

   A sore on the back or hips caused by lying for a long time in bed. [1913 Webster]

bedsore, n. a sore developed by an invalid because of pressure caused by lying in bed.