The Collaborative International Dictionary of English v.0.48:

Inpatient \In"pa`tient\, n.
   A patient who receives lodging and food, as well as
   treatment, in a hospital or an infirmary; -- distinguished
   from outpatient.
   [Webster 1913 Suppl.]

WordNet (r) 3.0 (2006):

inpatient
    n 1: a patient who is residing in the hospital where he is being
         treated [syn: inpatient, inmate] [ant: outpatient]