What is Flubbage?
The act of pressing your mouth to a loved one's (usually a child's) tummy and blowing hard so as to cause loud flatulent noises and great hilarity.
Dad: Just a little flubbage?
Daughter: Hee hee hee
Dad: FFFBBBLLLBBBFFFBBLLL
Daughter: HEE HEE HEEE HHHEEEEE - Stop!