In music, melisma is the process of singing more than one note while singing a single syllable of the lyrics of a song. The term originated with Gregorian Chants and baroque singing and carried on to gospel. Aretha Franklin is generally considered to be one of the better modern employers of the technique.
Adapted from the Internet-Encyclopedia article, "Melisma" Internet-Encyclopedia, article "Melisma" (http://www.internet-encyclopedia.org/wiki.phtml?title=Melisma)