An outpatient is someone who goes to a hospital or clinic for care and then goes home the same day. They do not sleep there. The person who stays overnight — or for many nights — is an inpatient, though actually everyday English often just says that person is “in hospital,” and saves outpatient for the clinic visit. You also hear it as a describing word: an outpatient clinic, outpatient surgery. That last one still surprises people: quite serious operations can now be outpatient, meaning you walk in, have the work done, and (if all goes well) sleep in your own bed. Doctors, hospitals, and insurance forms all use it; it is ordinary medical English, not slang. The out- here really is “outside the ward,” not “better than.”