Muff Daddy Share definition Flag n. an individual's (male or female) non-biological lesbian step-mother. "Portia de Rossi is my biological mother and Ellen Degeneres is my Muff Daddy" said Lady Gaga. Muff Daddy by retortme May 5, 2010 0 0 Get merch Get the Muff Daddy mug. Buy Now — $32.95 See more merch