Happy Birthday Bitch! Share definition Flag A phrased used to tell your best-girl "Happy Birthday". Girl 1: Happy birthday bitch! Birthday Girl: Thanks gurl, I'm gettin' fucked up tonight! Happy Birthday Bitch! by L-Breezy March 14, 2007 0 0 Get merch Get the Happy Birthday Bitch! mug. Buy Now — $32.95 See more merch