Distantly related to singing, the act of warbling the length and depth of the musical scale all on one note, ad nauseum. Usually culminating in screaming and/or screeching. Known to cause intense irritation and pain. See: Mariah Carey, Whitney Houston, Beyonce, Christina, etc.
I've had enough diva-howling to last a lifetime with all of those ads for WW and Jenny Craig and Nutrisystem and whatnot.