Bby Share definition Flag Short for "baby" used when you don't want to use such an intimate word but still want to call them that. ie. (Speaking to my new guy I'm dating but not my boyfriend yet) You're the best bby <3 Bby by miCalle June 11, 2020 0 0 Get merch Get the Bby mug. Buy Now — $32.95 See more merch