1. Relating to a hospital.
2. Denoting a new disorder (not the patient's original condition) associated with being treated in a hospital, such as a hospital-acquired infection.
The definition information for nosocomial is provided by Stedman's. You can search our medical dictionary here.
Stedman's, part of Lippincott Williams & Wilkins, provides a comprehensive line of health-science publications for healthcare professionals and medical students.