Decubitus

from WordNet (r) 3.0 (2006)

decubitus
    n 1: a reclining position (as in a bed)

from The Collaborative International Dictionary of English v.0.48

Decubitus \De*cu"bi*tus\, n. [NL., fr. L. de- + cubare, to lie
   down: cf. F. d['e]cubitus.] (Med.)
   An attitude assumed in lying down; as, the dorsal decubitus.
   [1913 Webster] Deculassement