Source : Webster's Revised Unabridged Dictionary (1913)

Bedsore \Bed"sore`\, n. (Med.)
   A sore on the back or hips caused by lying for a long time in
   bed.

Source : WordNet®

bedsore
     n : a chronic ulcer of the skin caused by prolonged pressure on
         it (as in bedridden patients) [syn: {pressure sore}, {decubitus
         ulcer}]