That would be when in an attempt to land, as you approach the runway & are beginning to bring her down to the ground the plane will balloon up on you. Or in other words it will rise up, sometimes quite violently. My friends Sukhoi would do it so bad it would take numerous attempts to get it on the ground. Each time he thought he had it, it would shoot back up from maybe 5 or 6ft off the deck to 20 to 30 ft in the blink of an eye. I think he was too tail heavy. This is the only way I know of that I've heard the term "Ballooning" used, I may be wrong or there maybe other ways in that this term is used, but this is the only one that I know of. Hope it helps some, more importantly I hope it is correct.[&:]