greasy mouth Share definition Flag A person who speaks loosely, dry snitches, smart mouths, simps, lames, haters and general dumb ass people. "Lisa a greasy mouth havin ass bitch. She was talkin bout business in front some random strangers." greasy mouth by KingStiff November 16, 2014 0 0 Get merch Get the greasy mouth mug. Buy Now — $32.95 See more merch