When a male/female toungue is in contact with the femal chest (usually nipples). Usually brings great pleasre to licker, and erotic pleasure to partner being licked.
Also see, sloppy second
As Penelope took off her tight shirt and i saw her huge rack, i got so hard. She then took off her bra and put my hand on her right tit. She proceeded to take my head and put it on her chest, almost demanding me to suck her warm tits, so i started titty sucking her.