From Wikipedia "A ritual of medical education, consisting of presenting the medical problems and treatment of a particular patient to an audience consisting of doctors, residents, and medical students. The patient is usually present for the presentation and may answer questions."
I once attended a Grand Round as a patient when I got malaria for the very first time.
Nicholas Genes at blogborygmi started the Grand Rounds of the medical blogosphere back in 2004. Rather like NHS Blog Doctor's weekly BritMeds but with a small difference in that each week a different medical blogger composes and hosts the Grand Rounds. The schedule and archives are available here.