rubella /ɹuːˈbɛlə/ noun1 •A mild disease caused by the Rubella virus infecting the respiratory tract, and characterised by a rash of pink dots, fever and swollen lymph nodes.At issue is the so-called MMR vaccine, which immunizes children against measles, mumps and rubella, three potentially deadly diseases that were once common and have been mostly wiped out. — 2002